SNC2D Physics – Light and Optics Optics Learning … or FALSE: RED light has a shorter wavelength...

SNC2D Physics – Light and Optics

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Optics Learning Goals

I am able to: 1. Light

a) Describe how light travels and what light is. b) Explain what an electromagnetic wave is. c) Draw an electromagnetic wave and describe the peak, trough and wavelength of a wave. d) Identify the portion of the electromagnetic spectrum that we can see. e) Describe the order of waves that make up the electromagnetic spectrum. f) Describe frequency and wavelength and how they are used to organize the electromagnetic spectrum. g) Describe the order of colours that make up the visible spectrum.

2. Production of Light

a) Explain the terminology used to describe the production of light; specifically incandescence, electric discharge, phosphorescence, fluorescence, chemiluminescence, bioluminescence, triboluminescence

b) Describe the difference between luminous and non-luminous objects and give a definition. c) Describe the behavior of light when it is reflected, absorbed, transmitted, refracted, diffracted. d) Describe the difference between transparent, translucent and opaque and be able to draw a picture to

describe them.

3. How light travels a) Draw a diagram which describes how images are seen in a pinhole camera. b) Explain how a pinhole camera is similar to a human eye. c) Define and draw a diagram for the following terms: incident ray, angle of incidence, reflected ray, angle

of reflection, normal, reflective surface,

4. Law of Reflection a) State the law of reflection. b) Relate the law of reflection to specular and diffuse reflection with diagrams.

5. Plane Mirrors

a) Describe what a plane mirror is and what happens when light hits a mirror. b) List the characteristics of images in plane mirrors. c) Describe how to identify a virtual image. d) Draw a diagram which describes how light rays travel from an object to the eye to allow you to see an

image in a plane mirror. e) Define lateral inversion. f) Describe what the acronym SALT stands for and how to determine each property.

6. Concave Mirrors

a) Draw a concave mirror diagram to scale and label the principal axis, focal point, vertex and the centre of curvature

b) Describe what the focal point is and how light has to hit the mirror to go through the focal point. c) Draw the four rays that can be used to identify the location of the image and briefly describe how they

occur. d) Locate the location of an image from the description of an object and the concave mirror. e) Give a practical application of concave mirrors.

7. Convex Mirrors

a) Draw a convex mirror diagram to scale and label the principal axis, focal point, the vertex and centre of curvature.

b) Describe what the focal point is and how light has to hit the mirror to go through the focal point. c) Draw the four rays that can be used to identify the location of the image and briefly describe how they

occur. d) Locate the location of an image from the description of an object and the convex mirror. e) Give a practical application of convex mirrors.


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8. Converging Lens a) State the difference between a mirror and a lens b) Draw a converging lens diagram to scale and label the principal axis, optical centre, optical axis, primary

focal point and secondary focal point. c) Describe how light has to hit the lens to go through the primary and secondary focal point. d) Draw the three rays that can be used to identify the location of the image and briefly describe how they

occur. e) Briefly describe the SALT for the following cases: beyond 2F, at 2F, between F and 2F, at F and in front

of F. 9. Diverging Lens

a) Draw a diverging lens diagram to scale and label the principal axis, optical centre, optical axis, primary focal point and secondary focal point.

b) Describe how light has to hit the lens to go through the primary and secondary focal point. c) Draw the three rays that can be used to identify the location of the image and briefly describe how they

occur. d) Briefly describe the SALT for the following cases: beyond 2F, at 2F, between F and 2F, at F and in front

of F. 10. Refraction

a) Define refraction. b) Draw a labeled diagram with the angle of incidence, incident ray, refracted ray and angle of refraction. c) Describe what a medium is. d) Describe why refraction occurs e) Describe what happens to light (with respect to the normal) when it travels from a more dense to less

dense medium. f) Describe what happens to light (with respect to the normal) when it travels from a less dense to more

dense medium. g) Describe what happens when light travels from one medium to another medium along the normal. h) Explain what the index of refraction is and know how to calculate it. i) Describe how index of refraction relates to the angles of incidence and angle of refraction. j) Describe how refraction relates to: apparent depth, a bent spoon, a mirage, the flattened sun and a

rainbow. 11. Total Internal Reflection

a) Describe what total internal reflection is. b) State the conditions for total internal reflection c) To describe, using diagrams, what happens to the refracted/reflected ray as the angle of incidence

increases. d) Explain what happens at the critical angle. e) Use Snell’s law to determine the critical angle when given the index of refraction for two materials.

I am able to read the question, identify given and unknown values and utilize the following formulas to solve a problem.

r

inθθ

sinsin=

vcn =

oi ddf111 +=

o

i

o

i

hh

ddM =−=


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Light and the Electromagnetic Spectrum What is light? § Light is ________and travels like a __________

§ A small packet of light energy is called a _______ § Light is a visible form of ______________radiation § Electromagnetic waves (including light) are made up of electrical energy and magnetic energy

§ Does not require a ___________ § Other types of electromagnetic waves: __________, ____________ waves, __________ See also http://www.colorado.edu/physics/2000/waves_particles/index.html Characteristics of a Wave § Waves have high points called “___________” § Waves also have low points called “__________” § The distance from one crest (or trough) to the next crest (trough) is called a “____________” § The distance from the centre line to crest or trough is the “_____________”

Figure 1. Characteristics of a wave.

The Electromagnetic Spectrum § A graph that shows the various type of electromagnetic

radiation (Fig. 3) § Arranged by wavelength and frequency

§ Wavelength: distance from peak to _______ or trough to _________

§ Frequency: the number of peaks that pass a point in a certain ____________

§ Also means _______ per second (measured in Hertz, Hz)

§ The longest waves are the ________ waves § The shortest waves are the __________waves NOTE: High frequency & short wavelength = HIGH ENERGY

Figure 3. The Electromagnetic Spectrum

Figure 2. Relationship between wavelength and frequency.

amplitude


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Visible Region of the Electromagnetic Spectrum § Light we can _______ § _________ – Acronym for: Red, Orange, Yellow, Green, Blue, Indigo, & Violet.

§ ________ to ________ Wavelength. Click here to see a prism separating white light

Figure 4. The Visible Spectrum

Key Facts About “Invisible Light” § All waves shorter than visible light can cause __________.

§ UV - light - sun burn and skin cancer § X-rays can cause cancer (that is why the dentist leaves the room when she X-rays your teeth)

§ ________ rays are the most dangerous

§ they can _______ ALL living things and cause cancer § BUT also used to _____cancer because they ______ cancer cell

Try These 1. Draw 3 complete cycles of a wave that has a wavelength of 2.0 cm. 2. Count the number of crests and troughs in the wave you drew from Q#1. Label each crest and trough. 3. What characteristic(s) of a wave is used to arrange the waves in the electromagnetic spectrum? 4. What is the visible spectrum? 5. What does the acronym ROYGBIV stand for? 6. TRUE or FALSE: Ultraviolet light has higher energy than microwaves? 7. TRUE or FALSE: RED light has a shorter wavelength than BLUE light? 8. Although gamma rays are very dangerous, they have a very important use. What are gamma rays used for? Homework Question For each type of wave listed in the previous slides (e.g. radio, microwave, etc…) summarize 2-3 uses of that type of wave. Use the Internet and your general knowledge to locate the information you need. [Thinking]

Type of EM Wave Use/Phenomena


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Class Discussion [Application] NASA: The Electromagnetic Spectrum • Go to the NASA: Electromagnetic Spectrum website posted above. • Spend approx. 5 minutes reviewing each of the different types of electromagnetic waves: Radio waves,

Microwaves, Infrared, Visible Light, Ultraviolet, X-rays, Gamma rays. • Choose 1 and identify

o its physical characteristics, and o example of something equivalent in size and o one thing it is used for in every day life.

• Post the answers on the Class Discussion thread called "Useful Radiation". Once you have posted, check some answers of your fellow classmates and comment on at least 2 other posts.

Additional Homework Questions Consider the electromagnetic spectrum as you answer these questions. 1. Name the region of the electromagnetic spectrum with the shortest wavelength. 2. Name the region of the electromagnetic spectrum with the lowest frequency. 3. Which region of the electromagnetic spectrum has the highest frequency? 4. Which region of the electromagnetic spectrum has the longest wavelength? 5. Which region of the electromagnetic spectrum will travel with the fastest speed? 6. Which region of the electromagnetic spectrum is the most energetic? 7. Consider the visible light spectrum as you answer these two questions.

o a. Which color of the visible light spectrum has the greatest frequency? o b. Which color of the visible light spectrum has the greatest wavelength?

8. Label the following diagram.

What is Light? List five properties of light (not a complete list):

• • • • •

Explain how light is produced: Define luminous à Define nonluminous à Distinguish between natural and artificial light:


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Types of Light Complete the following table. Type Description of how it works Examples/Uses 1.

2.

3.

4.

5.

6.

7.

8.


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How Light Interacts With Objects Light Rays • When you look at an object, you see it because light travels in a _______ line from the object to your eyes. • Scientists use an __________ to trace the path and show the direction that light travels • The arrow is called a ______________ Reflection • Reflection is the process in which light “_________________” a surface and changes _____________

• Light rays travel from a ______________, the lamp, and ___________ from the paper to your eyes. Absorption • ____________ is the process in which light energy remains in an object and is converted into

_____________.

• Black print on a page ________ all light and therefore no light reaches the eye. Your brain interprets the

____________ of light as black

Transmission • _____________ is the process in which light _____________ an object and keeps

travelling, allowing you to see the objects on the other side. • Clear glass and plastic ___________ light • White paper transmits ___________ light and reflects or absorbs the rest • Transparent: Light is transmitted without any change in _________.

o Example: clear glass • Translucent: Light can pass but is ____________ in many different directions. You

cannot see a _____ image on the other side. o Example: waxed paper

• Opaque: No light __________ therefore all light is either reflected or absorbed. o Example: Wood

Refraction • Light rays appear to “_________” when travelling from one medium to another • Examples include:

o Refraction through a __________ (Dispersion) o Corrective glasses o Fish appear at a different position in aquarium


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Diffraction • Diffraction is:

o the apparent ____________ of waves around small obstacles and o the ____________ out of waves past small openings


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Pinhole Camera Lab


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The Ray Model of Light Light Rays • Light travels in a ____________ _____________ • A light ray is a ___________ and ___________ representing the

___________ and straight-line path of light • Because the candle to the right is radiating light in all _____________, an

____________ number of light rays are coming from the candle Terminology • Incident Light à light emitted from a source that ___________ an object • Image à ______________ of an object through the use of light • Mirror à any polished surface ______________ an image (see below) • Reflection àthe ____________ _________ of light from a surface

• The ray of light approaching the mirror is the ___________ ray • The ray of light which leaves the mirror is the ___________ ray • A line drawn perpendicular to the surface of the mirror at the point of incidence where the ray strikes the

mirror, is known a ______________ line • The angle between the incident ray and the normal is the angle of ______________ • The angle between the reflected ray and the normal is the angle of _______________ Homework Answer the following questions:

1. What did you notice in today’s lab about the angle of incidence and angle of reflection? 2. Draw a sketch based on today’s lab and label the following: mirror, normal, incident ray, angle of

incidence, reflected ray, and angle of reflection. 3. In one sentence, summarize the relationship between the angle of incidence and the angle of reflection. Be sure to use the same vocabulary used in your sketch.


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Reflection The Law of Reflection When a ray of light reflects off a surface, the angle of ___________ is equal to the angle of ___________. This relationship can be described mathematically as:

𝜃! = 𝜃!. Smooth vs. Rough Surfaces • When light rays reflect off of a smooth surface, they do so in

the same pattern as the ___________ rays. o This produces a ___________ image.

• When light rays reflect off of an irregular or dull surface, the pattern of reflected rays is ___________ than the pattern of incident rays.

o This produces a __________ or unclear image. Angles Complete the activities on this website to practice measuring angles with a protractor:

http://www.mathsisfun.com/geometry/protractor-using.html

What’s that law again? • ___________ reflection occurs when light is reflected off a smooth shiny surface • Because light travels in straight lines;

o The angle that light strikes the surface (__________________________) is the same as the angle that light leaves the surface (__________________________).

Terminology _________________: light which travels towards the mirror __________________: light which is reflected by (bounces off) the mirror ___________: imaginary line drawn at 90 degrees to the mirror surface ________________________: angle between the incident ray and normal ________________________: angle between the reflected ray and normal Diagram Draw a diagram to explain the law of reflection in the space below.

Figure 5. The law of reflection states that the angle of reflection is equal to the angle of incidence.

normal

Figure 6. Specular versus diffuse reflection.


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Law of Reflection 1. The angle of reflection ____________ the angle of incidence. 2. The incident ray, reflected ray and normal all lie in the same _____________. Real or Virtual Image? In plane mirror reflection, a _____________ image is formed. A _____________ image is an image formed by rays that do not actually pass through the location of the image. Image Characteristics In optics, we will describe the characteristics of an image using the acronym L.O.S.T. L - ______________ O - ______________ (upright or inverted) S - ______________ (magnified, reduced, same size) T - ______________ (real or virtual) In the table below, write a summary of the image characteristics for a plane mirror.

L

O

S

T

Figure 8. Image characteristics for a plane mirror.

Homework Complete any parts of the Multiple Images lab not finished during class and make sure you fill out the table above.

Figure 7. Virtual image produced by a plane mirror.


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Copyright 2005 by The International Society for Optical Engineering (SPIE), The Optical Society of America (OSA), and The Association of Universities for Research in Astronomy, Inc. (AURA). All rights reserved.

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STUDENT HANDOUT: Multiple Reflections What You Need � 1 set of hinged mirrors � 1 copy of “The Pirate Handout” � 1 protractor What To Do 1. Open the hinged mirror and look into it. Slowly change the angle and observe the number of

reflections of yourself that you see. If you want to see more reflections, do you make the angle between the mirrors larger or smaller?

2. Place the large R on the table. Open the mirror and place

it on the R as shown in the picture at right. Adjust the angle between the mirrors until you see exactly one complete reflection of the R in each mirror. (You will see three R’s – the original plus two reflections.) Use your protractor to measure the angle between the mirrors and record it in the data table on the next page. In the last column, sketch the pattern you see similar to the sketch below.

3. Move the mirrors until you see three complete reflections of the R in

the mirrors. Measure the angle of the mirrors and record the angle in the data table below. In the last column, sketch the pattern you see. Be sure to pay attention to which images of the R are reversed and which are not.

4. Repeat moving the mirrors, increasing the number of reflected R’s by one each time, until

you see 7 reflections. 5. Create a graph of the number of reflections (y-axis) versus mirror angle (x-axis). Describe

the shape of the graph in words.

THIS PAGE MAY BE PHOTOCOPIED FOR CLASSROOM OR WORKSHOP USE


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6. By looking at your data and at the graph, see if you can predict the angle between the mirrors when you would see eight reflections. Predict the angle for nine reflections.

7. Can you come up with a formula that relates the number of reflections you see to the angle

between the mirrors?



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DATA TABLE

Number of Reflections Angle Between Mirrors Sketch



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Properties of Plane Mirrors Image Formation in Plane Mirrors • An eye catches rays ___________ from mirror. • Observer has a sensation that image is _________ the mirror.

There is nothing behind the mirror. • There is no light going to or coming from behind the mirror. Light

only __________ to be coming from the image. • This image is ___________, or a ___________ image. Properties of Images Formed by Plane Mirrors Location - Image is at the same distance from mirror as the object (di/do = 1) Orientation - The image is __________ but laterally __________ (Left / Right) Size - The image has the ___________________ as the object (hi/ho= 1) Type - Plane mirrors form __________ images (no real light is there) Image Formation in Plane Mirrors – Point Objects • Both green and red rays, coming out of point A, are reflected such

as 𝜃! = 𝜃!. • Their _____________ meet at A’ behind the mirror. • The image is formed at the point where the extensions of the

reflected rays _____________. • Due to the symmetry of the diagram about the mirror surface, 𝑑! = 𝑑!

and AA’ ┴ mirror • See this link

• No matter where the observer is, due to the symmetry on the diagram to the left, all the extensions of reflected rays meet at the same point, A’, which is:

• ____________ the mirror • on the _______________ line passing through

the object • at the same distance from the mirror as the

object THEREFORE: ____ rays are enough to locate the image

do

di A’ A

do d

i

A’ A


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Drawing Ray Diagrams in Plane Mirrors Draw an object (use an arrow) that is 6 cm tall. Draw this object 10 cm from a plane mirror.

Locate extreme points on the object. For EACH of the extreme points: 1. Draw a light ray perpendicular to the mirrored surface. This light ray reflects back on itself (Represent

this using arrowheads). Extend this reflected ray behind the mirror. 2. Draw a second light ray from the point to anywhere on the mirror. Draw in a normal line where the

incident ray meets the mirror. Measure the angle of incidence. Draw in the reflected ray, where the angle of incidence equals the angle of reflection. Extend the reflected ray behind the mirror.

3. Where the two reflected rays meet that originated from the same point on the object is where the image of that point will be formed.

4. Connect the image by using the two extreme points you found. Example:


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SEEING IMAGES IN PLANE (FLAT) MIRRORS 1. Show how the Eye/Brain “sees” the Image of the Object in the diagram below

2. Show how the Eye/Brain “sees” the Image of the Object in the diagrams below


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3. Which Eye/ Brains can see the Object?

4. Which Eye/ Brains can see the Image? Full Body Mirror 5. How big does a Mirror have to be in order to see yourself “Head to Toe”? (Hint You see

your image) 6. If you can just read the Middle line of an Eye Chart taped onto a Mirror. Which line of the

same sized Eye Chart could you read when viewed in a Mirror? Would it be, a) one Line up (2X’s Larger) b) the same line c) one line down (Smaller by half)


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SNC2D0

Plane Mirror Practice Questions 1. An object 4 cm high is located 15 cm in front of a plane mirror. List the four image properties of this image.

L-

O-

S –

T -

2. A student stands 3 m in front of a plane mirror on his head

a) What is attitude of the image?

b) How far behind the mirror is the image?

c) How far from his image is he?

d) If he moves ahead 1m how far will he be from his image?

3. A student approaches a plane mirror at a speed of 2 m/s.

a) at what speed does her image approaches the mirror?

b) at what speed does she approach her image?

4. What is the real time if the time on a clock (with no numbers) appears to read the following times when viewed in a plane mirror?

a) 8:00 b) 7:30 c) 6:00 d) 3:00


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Ray Diagrams and Plane Mirrors


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Name:_______________________

Concave Mirrors Lab

Terminology: Part A: Concave Mirrors 1. Set-up the ray box for 5 rays and adjust until rays are parallel. 2. On a blank sheet of paper, draw a line for the principal axis of the mirror. 3. Place the mirror on the principal axis and mark its position on the paper. 4. Use the ray box to send 5 parallel incident rays on to the mirror. Place the centre

ray on the principal axis. The position where the 5 rays are focussed into a point is called the focus or focal point.

5. The distance from the vertex to focus of a mirror is called the focal length. 6. Measure the focal length of your mirror. Focal length (f) = ____________ 7. Make a neatly labelled diagram showing the concave mirror (with reflective

surface), its principal axis, the vertex, focal point, focal length, incident rays and reflected rays

Part B: Four principal rays for a Concave mirror 1. On a blank sheet of paper, draw a line to represent the principal axis. Place a

concave mirror on the axis and mark its position. 2. Use a ray box to locate the focal point for the mirror. Mark the position on your

diagram. 3. The centre of curvature for a mirror is located on the principal axis at a distance of

twice the focal length from the vertex in front of the mirror. (i.e. C = 2 x f) Mark the centre of curvature for your mirror on your diagram.

Principal axis

Concave Mirror

vertex


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4. In each of the following mark the path of the reflected ray for each of the given incident rays (use the plate that only has one slit)

a) incident ray parallel to principal axis b) incident ray passing through the focus

c) incident ray passing through the d) incident ray striking the vertex centre of curvature

Incident rays parallel to the principal axis are reflected in such a way that the reflected rays …

Incident rays passing through the focus are reflected in such a way that the reflected rays …

Incident rays passing through the Centre of Curvature are reflected in such a way that the reflected rays …

Incident rays striking the vertex of the mirror are reflected in such a way that the reflected rays …


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Concave Mirrors Spherical Mirrors • A spherical mirror has the shape of a section of a sphere. • If the outside is mirrored, it is __________. • If the inside is mirrored, it is _________. (Fig. 1) Concave & Convex Mirrors • For a concave mirror, both the focal point (F) and the centre of curvature (C)

are in front of the mirror. • For a convex mirror, both the focal point (F) and the centre of curvature (C) are

behind the mirror.

Focal Length – Concave Mirrors • Parallel rays hitting a spherical mirror come together (intersect) at the

__________ • Focal point, F, is _____________ the mirror • The distance from the focal point to the vertex of the mirror is the

_______________, f Terminology

Figure 1

. Concave and convex mirrors.

Incoming light ray

Figure 2. Concave mirror.

Incoming light ray

Figure 3. Convex mirror.


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Constructing Ray Diagrams 1. P ray: A light ray parallel to the principal axis is reflected through the ___________. This is how the focus is

defined. 2. C ray: A light ray through the centre of curvature is reflected back ___________________. This rule makes

sense because any line through the centre of curvature is a radius of the circle formed by the mirror. A radius is always at 90° to the mirror. A ray along the normal has an angle of incidence of 0°. This means that the angle of reflection is also 0°. The reflected ray will return back on the same path.

3. F ray: A ray through F will reflect ____________ to the principal axis. This rule uses the fact that the angle of incidence is always ____________ to the angle of reflection. Even if you switch the incident and reflected rays, the light will still follow the same path; only the direction will change. This principle is called the _______________ of light.

4. V ray: A ray aimed at the vertex will follow the law of _____________. Because the principal axis is perpendicular to the surface of the mirror, the angle of incidence can be easily measured (not widely used as it requires the use of a protractor).

Summary:

How do we see an image? • A point object emits (or reflects) light in all _____________ • All the rays reflected by the mirror meet at one ___________ • Eye detects the light that hits the __________ Ray Diagrams for a Point Source

• No need to draw that many rays to find the image • Draw any two out of four ________ rays originating from the point object • Image is located at the intersection of their ______________ rays • Any other reflected rays will ______________ at this point as well

Ray Diagrams for a Non-Point Source • For non-point objects, use ____________ points (as in plane mirrors) • IMPORTANT - Any point on axis will form image on ___________.

Incident Ray Reflected Ray

Parallel to principal axis

Through the focal point

Through C

Through vertex θ

O

O’

O

O’


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Concave Mirror Image Properties Summary

Object location (do) Location Orientation Size Type

Beyond C

At C

Between F and C

At F

Between F and the Mirror

Scale Ray Diagrams A pencil 15 cm high is located 60 cm in front of a concave mirror with a focal length of 20 cm. Construct a scale diagram to correctly determine the location of the image and its height. [Thinking] (indicate the scale used) Ray Diagram Practice 1. Mark and label the focal point and the centre of curvature of the mirror in this diagram.

2. What is the orientation of the image when an object is located between a concave mirror and its focal point? 3. What is the orientation of the image when an object is located between the focal point and the centre of

curvature of a concave mirror? 4. Is it possible for the image to be upright when an object is 30 cm away from a concave mirror with a focal

length of 25 cm? Explain your reasoning. 5. A concave mirror has a focal length of 5 cm. An object 2 cm high is 11 cm from the mirror. Draw a scale ray

diagram. Measure the image height and image distance. Homework: Complete the Concave Ray Diagram sheet, along with the above question


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Convex Mirrors • For a convex mirror, both F and C are behind the mirror • Because of this, the mirror has a negative focal length

Constructing Ray Diagrams When constructing ray diagrams with convex mirrors, use the same principle rays as for concave mirrors. The principle rays are shown below.

5. P ray: A light ray parallel to the principal axis is reflected as if it had come through the ___________. 6. C ray: A light ray aimed at the centre of curvature is reflected back ___________________. 7. F ray: A ray aimed at the focus (F) is reflected ____________ to the principal axis. *Always remember that when locating an image, ALL RAYS ORIGINATE FROM THE ___________!

Convex Mirrors Focal Point For convex mirrors: • Parallel rays hitting a spherical mirror ___________ to come together (intersect) at the focal point • Focal point, F, is _____________ mirror • 2F = C Note: use dotted lines to represent “imaginary” light rays Image Formation Using Ray Diagrams for a Convex Mirror

Figure 9. A convex mirror has F and C behind the mirror, and a negative focal length.

Figure 10. Principle rays for a convex mirror.

Figure 4. Projections of reflected P, C, and F rays cross at the location of the image.


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Image Properties

Location

Orientation

Size

Type

*Note: For a convex mirror, image properties are the _____________ regardless of object location. See animation

• For a convex mirror, rays from the object will ______________ (i.e. spread out) upon being reflected, thereby appearing to originate ______________ the mirror.

• The image is located where the ________________ (dashed lines) of the three rays cross (intersect). Use dashed lines to extend rays behind mirror.

• The size of the image can be determined if you draw your diagram to _____________. LOST for Concave vs. Convex Mirrors Concave Mirror Convex Mirror

Location

Location

Orientation

Orientation

Size

Size

Type

Type

*Image properties depend on object location *Image properties are the same regardless of object location

Try One! An object 5 cm high is placed 10cm in front of a convex mirror with a focal length of 20cm. Using a scale ray diagram identify the characteristics of the image. Homework:

- Complete the above practice question if not done already - Convex mirrors ray diagrams sheet – complete all diagrams and LOST for each - Concave mirrors problem set – due Nov. 1

Figure 5. Locating an image produced by a convex mirror.


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Object Position

Ray diagram Image properties

Beyond C

L _____________ O _____________ S _____________ T_____________

At C

L _____________ O _____________ S _____________ T_____________

Between F and C

L _____________ O _____________ S _____________ T_____________

At F

L _____________ O _____________ S _____________ T_____________

Between F and Mirror

L _____________ O _____________ S _____________ T_____________


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Object Position


Beyond C

L _____________ O _____________ S _____________ T_____________

At C

L _____________ O _____________ S _____________ T_____________

Between F and C

L _____________ O _____________ S _____________ T_____________

At F

L _____________ O _____________ S _____________ T_____________

Between F and Mirror

L _____________ O _____________ S _____________ T_____________

C

F


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Concave Mirrors Ray Diagrams Problem Set Each diagram must have:

• principal axis and a mirror (use a protractor to trace a curved surface). Reflective side of the mirror must be made clear (shading)

• an object represented as an up-right arrow with an appropriate (to scale) height • a scaled ray diagram showing two principal rays coming out of the object’s extreme

point. • the image at the intersection of the reflected rays • Using scale, identify image properties and answer the questions.

1. A nail 5 cm high is in front of a concave mirror 5 cm beyond the focal point. If the focal

length of the mirror is 15 cm, what is the size of the image formed?

2. A candle 7 cm high is placed 15cm away from the vertex of the concave mirror with the focal length 25 cm.

a. What is the location of the image? b. What is the size of the image?

3. A person eating cereal happens to peer into his spoon. If his face is 18 cm from the spoon

and is 21cm long. The focal length of the spoon is 3 cm: a. how far from the spoon is the image? b. measure the size of the image

An object 10cm high is placed 15cm in front of a concave mirror with a focal length of 5 cm. Identify all the characteristics of the image.


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Converging (Convex) and Diverging (Concave) Lenses Terminology: Part A: Convex Lenses 8. Set-up the ray box for 5 rays and adjust until rays are parallel. 9. On a blank sheet of paper, draw a line for the principle axis of the lens and a line for

the optic axis (see diagram above). USE A RULER! 10. Place the converging lens on the principle axis and mark its position on the paper. 11. Use the ray box to send 5 incident rays through the lens. Place the centre ray on the

principle axis. 12. Define: Focal point –

Focal length –

13. Measure the focal length of your lens using a ruler. Focal length (f) = ____________

14. Why does any lens have two focal points? 15. Make a neatly labelled diagram, using a ruler, of the converging lens showing the

principal axis, the vertex, BOTH focal points, focal length, incident rays and refracted rays.


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Part B: Principal Rays for a Convex Lens 5. Using the other side of your paper, draw a line to represent the principle axis. Place

a converging lens on the axis and mark the position of it. (hint: trace the same lines as on the other side of the page if possible)

6. Use a ray box to indicate the position of both focal points for the lens. Mark these positions on your diagram.

7. Set up your ray box for a single ray and use the diagrams below to direct your rays. 8. Complete each of the following diagrams by marking the path of the refracted ray

for the given incident rays and complete the summaries:

Part C: Diverging (Concave) Lenses 1. Repeat steps 1 to 4 above using a diverging lens. 2. How do you locate the focal point for this lens? 3. Measure the focal length of your lens. Focal length = _______________ 4. Make a neatly labelled diagram of the convex lens showing the principal axis, the

vertex, focal point, focal length, incident rays and refracted rays.

Concave Lens

Incident rays parallel to the principle axis are refracted in such a way that the refracted rays …

Incident rays passing through the vertex are refracted in such a way that the refracted rays …

Incident rays passing through the focal point are refracted in such a way that the refracted rays …

Incident rays passing through F are refracted in such a way that the refracted rays …


37

Converging and Diverging Lenses What are lenses? • Lenses are used to ___________ light and form ____________. • There are a variety of possible types • We will consider only the _______________ ones

o the double ___________ and the double _____________

Converging at the Focal Point • For a double convex (i.e. _____________) lens, the light refracts such that it converges at the focal point.

Diverging from the Focal Point • A double concave (i.e. ______________) lens has the refracted rays diverging as if they all come from the

focal point.

Constructing Ray Diagrams Draw of the principal rays originating from the same on the object and follow these rules: • 1. P-Ray is drawn through a point on the object and _____________ to the principal axis.

o It is refracted through the ___________________, F. • 2. F-Ray is drawn through a point on the object and through (convex) or towards (concave) the

_________________. o it is refracted ______________ to the principal axis.

• 3. V-Ray is drawn through a point on the object and through the ____________. o It goes straight ___________ and does NOT change ___________ (assuming lens is thin)


38

Converging Lenses • Converging = ______________ • The convex lens forms different image types depending

on where the object is located with respect to the __________________

• 5 possible object locations 1. Case 1: The object is located in front of F 2. Case 2: The object is located at 2F 3. Case 3: The object is located beyond 2F 4. Case 4: The object is located between F and

2F 5. Case 5: The object is located at F, the focal

point. • Please complete handout for CONVEX lenses (front half)

(two examples are done for you on the next slides to help get you started) Diverging Lenses • Diverging = _______________ • Complete the ray diagrams for concave/diverging lenses • You only need to complete two or three of these … if you catch on to the trend, you can stop

Summary: Image Characteristics formed by Concave and Convex Lenses

Concave Lens (Diverging)

Object Location Size Attitude Location Type

Arbitrary

Convex Lenses (Converging)

Object Location Size Attitude Location Type

Beyond 2F

At 2F

Between F and 2F

At F

In front of F

Homework • Complete ray diagrams and fill in table above


39

Ray Diagrams for Converging Lenses

Object Position


Beyond 2F

L _____________ O _____________ S _____________ T_____________

At 2F

L _____________ O _____________ S _____________ T_____________

Between F and 2F

L _____________ O _____________ S _____________ T_____________

At F

L _____________ O _____________ S _____________ T_____________

Between F and Lens

L _____________ O _____________ S _____________ T_____________


40

Ray Diagrams for Diverging Lenses

Object Position


Beyond 2F

L _____________ O _____________ S _____________ T_____________

At 2F

L _____________ O _____________ S _____________ T_____________

Between F and 2F

L _____________ O _____________ S _____________ T_____________

At F

L _____________ O _____________ S _____________ T_____________

Between F and Lens

L _____________ O _____________ S _____________ T_____________


41

Problem Set: Lenses 1. A 16mm high object is viewed with a converging lens of focal length 32 mm. For each

object distance listed below: a. draw a scaled ray diagram using all the rules to locate the image of the object b. State the characteristics of each image (LOST)

i. do = 64 mm ii. do = 52 mm iii. do = 16 mm

2. Below is a list of optical devices. For each of the following cases, explain what kind of

lens must be used and where the lens must be placed relative to the object: a. A copy camera produces an image that is real and the same size b. A slide projector produces an image that is real and larger c. A spotlight produces parallel light; there is no image d. A photographic enlarger produces an image that is real and larger

3. A pencil 15 cm high is placed 45 cm in front of a converging lens with a focal length of

12 cm. Using a scale ray diagram find: a. The distance from the lens to the image [16 cm] b. The distance from the object to the image [61cm] c. The image height [5.3 cm]

4. For the object and distances from Question 1, calculate di using the thin lens equation

and calculate your percent error.

5. For the object in Question 3 calculate di and your percent error.

6. An image formed by a diverging lens is only ¼ as far from the lens as the object. Find the distance from the image to the lens if the focal length is 30 cm. [38cm]

7. The sun is 1.49X 1011 m from the earth. A converging lens with a focal length of 32cm

is used to form an image of the sun. a. How far from the lens is the image formed? [32 cm] b. How might you have guessed this result without even performing the calculation?

8. A tree 11cm from a converging lens forms an image 78cm from the lens. Calculate the

focal length of the lens. [73cm]

9. A projector lens has a focal length of 25cm. A 35mm slide is placed 26 cm from the converging lens. a. How far away from the lens must the screen be positioned? [650 cm] b. What is the size of the image formed on the screen? [875 mm]

10. An object is 3 times the distance to a converging lens as its image is. If the focal

length of the lens is 25 cm, how far from the lens is the object? [100cm]


42

Refraction Lab


43

+ Text Only Site+ Non-Flash Version+ Contact Glenn

Table of Sin(a) http://www.grc.nasa.gov/WWW/k-12/airplane/tablsin.html

1 of 2 16/10/2012 9:47 AM


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Refraction What is refraction? • The ___________ or change in ____________ of light as it passes from one substance (medium) to another

substance (medium) of differing ______________ Why does light bend? • Refraction happens because the light slows down in the new material

Rules of Refraction • Speed of light changes depending on the ________________ through

which it is travelling • The angle of refraction is the angle between the _____________ ray

and the normal • Light bends toward the normal when the speed of light in the second

medium is __________ than the speed of light in the first medium • Light bends away from the normal when the speed of light in the

second medium is ___________ than the speed of light in the first medium

Practice • In each diagram, draw the "missing" ray in order to appropriately show

that the direction of bending is towards or away from the normal.

Basic Properties of Refraction • When a ray of light enters a medium where its speed decreases, it is bent __________ the normal. • When a ray of light enters a medium where its speed increases, it is bent ___________ the normal • There is no change in __________ if there is no change in the index of ___________. The greater the

change in index of refraction, the ____________ the change in direction.

Figure 11. When the wagon travels from pavement to sand, its right front wheel hits the sand first, causing it to slow down. Since the left front wheel is moving faster than the right front wheel, the wagon turns to the right.


45

• If a ray of light goes from one medium to another along the ___________, it is not refracted, regardless of the index of refraction

The Bent Spoon • The spoon looks broken in a glass of water • The light rays bend as they go from the air into the water in the glass • The pattern of the light rays gets distorted due to refraction

The Index of Refraction � The ratio of the speed of light in a ___________ (c) to the speed of light in a __________ (v) is called the

index of refraction and is represented by the letter n.

𝑛 =𝑐𝑣

� This is a physical property of the substance (like melting and boiling point) c = speed of light in a vacuum (3.00 x 108 m/s) v = speed of light in the material

Practice What is the index of refraction of a liquid in which the light travels at 2.04 x 108 m/s? The Refraction of Light Here are some typical indices of refraction:


46

Snell’s Law � The ratio of the sine of the angle of incidence to the sine of the

angle of refraction is constant (for the same medium):

sin 𝜃!sin 𝜃!

= 𝑛

where θi is the angle of incidence and θr is the angle of refraction.

� We can now write the angle of refraction in terms of the index of refraction:

𝑛! sin 𝜃! = 𝑛! sin 𝜃!

� This relationship is known as ___________________. � Note: the incident ray and the refracted ray are on ____________ sides of the normal Practice 1. If light passing from water to glass has an angle of refraction of 32°, find the angle of incidence. (nglass = 2.42

and nwater = 1.33) 2. Calculate the angle of refraction in the diagram below. nair = 1.00; nwater = 1.33

3. Calculate the angle of refraction in the diagram below. nair = 1.00; nglass = 1.52

Refraction of Light Problems 1. The speed of light in glass is 2.0 x 108 m/s. Calculate the index of refraction for the glass. 2. If light passing from water to glass has an angle of refraction of 25°, find the angle of incidence. (nglass = 1.46

and nwater = 1.33) 3. The index of refraction for ethanol is 1.37. Calculate the speed of light in ethanol. 4. The angle of incidence in diamond is 20°. What is the angle of refraction in air? 5. The speed of light in leaded glass is 1.66 x 108 m/s. That is the index of refraction for this type of glass? 6. The speed of light through a material is 1.24 x 108 m/s. What is the material? 7. Light travels from air (n=1.00) into an optical fiber with an index of refraction of 1.44. If the angle of

incidence on the end of the fiber is 22o, what is the angle of refraction inside the fiber? 8. What is the speed of light through alcohol?


47

Phenomena Related to Refraction Summarize the following phenomena using internet research � Apparent depth � The flattened Sun � Mirages • The rainbow Homework • Refraction problems from above • Post to the class discussion for the Snell’s Law Lab • Curved mirror problem set due Feb 18 Total Internal Reflection • When light travels between media, some light is ____________ and some is _____________ • Light bends ________________ the normal when it speeds up at the boundary of two media

o Angle of refraction is larger than the angle of incidence (Fig. 1) Critical Angle • The angle of refraction continues to increase as the angle of _____________ increases. • Eventually, the angle of refraction will become ___________ (Fig. 3)

o At this point, the angle of incidence is called the _______________________ • If the angle of incidence is increased __________ the critical angle, the refracted ray will not exit the medium

(Fig. 4) o It will ___________ back into the medium o This is called ________________________________

Click HERE Conditions for TIR • Total internal reflection occurs when 2 conditions are met:

o Light is travelling more ___________ in the first medium than in the second o The angle of incidence is larger than the critical angle

Calculating Critical Angle Use Snell’s law to calculate the critical angle for a water -> air boundary. Homework • Complete virtual lab • Post one TIR application to class discussion

Figure 14. Incident ray at less than the critical angle.

Figure 14. Incident ray at the critical angle.

Figure 14. Total internal reflection occurs when the angle of incidence is greater than the critical angle.


48

The Thin Lens Equation Converging/Convex Lenses • In convex lenses,

o f is ____________ o do is always _____________ o di can be ____________ or ______________

Diverging/Concave Lenses • In concave lenses,

o f is ___________ o do is always ___________ o di is ___________

The Thin Lens Equation The thin lens equation is: Where f is the __________ __________, d0 is the distance from the _____________ to the lens, and di is the distance from the ____________ to the lens. • To use the thin lens equation, you need to follow this sign convention:

o Object distances (do) are always __________ o Image distance (di):

o Are __________ for real image (image is opposite side of lens as object) o Are __________ for virtual images (when the image is on the same side of the lens as object)

o The focal length (f) is _________ for converging lenses and ________ for diverging lenses. Sample Problem Calculate di for the following diagram.


49

Calculating Percent Error • You can check the accuracy of your drawings by comparing your ________________ to your calculations.

o Theoretical is the image distance you _____________ using the thin lens equation o Experimental is the image distance you _____________ on your scale ray diagram o If you get a negative percent – just ignore the negative sign.

Homework • Lenses Problem Set questions 4-11 • Snell’s Law & Thin Lens review practice sheets

�

%error =theoretical − experimental

theoretical⎛ ⎝ ⎜

⎞ ⎠ ⎟ x100%


50 550 Skills Reference 12 Optics

Snell’s LawSnell’s law relates the indices of refraction ofa material to the angles of incidence andreflection.

It uses values for the index of refraction tocalculate the new angle that a ray will take asa beam of light strikes the interface betweentwo media.

If you call the indices of refraction of thetwo media n1 and n2 and call the angle ofincidence and the angle of refraction θ1 andθ2, then the formula for Snell’s law is:

n1sinθ1 = n2sinθ2

A table of indices of refraction for selectedsubstances can be found below.

Instant Practice1. When light passes from air into water at an

angle of 40° from the normal, what is theangle of refraction?

2. When light passes from water into sapphire atan angle of 35° from the normal, what is theangle of refraction?

3. When light passes from air into Plexiglas atan angle of 15° from the normal, what is theangle of refraction?

4. When light passes from air into water at anangle of 30° from the normal, what is theangle of refraction?

5. When light passes from water into sapphire atan angle of 45° from the normal, what is theangle of refraction?

6. When light passes from air into Plexiglas atan angle of 20° from the normal, what is theangle of refraction?

Substance Index of Refraction

air 1.0003

water 1.33

Plexiglas 1.49

sapphire 1.77

Index of Refraction for Selected Substances

Example Problem 12.2When light passes from air into water atan angle of 50° from the normal, what isthe angle of refraction? Identify air asmedium 1 and water as medium 2.

GivenIndex of refraction of air = n1 = 1.00Index of refraction of water = n2 = 1.33Angle of incidence θ1 = 50°

RequiredAngle of refraction = nθ2

Analysis and SolutionThe correct equation is sinθ2 = Substitute the values and their units, and solve the problem.

sinθ2 =

= ( )

= sin–1 ( )

= 0.58

Therefore, θ2 = 35°

ParaphraseThe angle of refraction is 35°.

1.00 ! 0.77 1.33

1.00 ! sin(50°) 1.33

n1sinθ1n2

n1sinθ1n2

Skills Reference 12


51 551Skills Reference 12 Optics

The Thin Lens EquationThe thin lens equation relates three qualitiesabout thin lenses:

• do – distance from lens to object

• di – distance from lens to image

• f – focal length of the lens.

The relationship takes the form of anequation, called the thin lens equation:

= +

Remember that for convex lenses, somedistances are taken to be negative. The tablebelow shows these:

1di

1do

1f

Skills Reference 12

Instant Practice1. A powerful magnifying glass produces a real

image 5 mm from the convex lens. If theobject was placed 35 mm away, what is thefocal length of the lens?

2. A concave lens has a focal length of 12 cm.An object placed 8 cm away is virtual,upright, and smaller. What is the distance ofthe image from the lens?

3. A convex lens with a focal length of 25 mmproduces an image 30 mm from the lens.How far from the lens is the object?

4. Determine the focal length of a convex lensthat produces a virtual image at a distance of40 mm, when the object is placed 20 mmaway.

5. A convex lens focusses the light from abacterium that is 0.030 cm from the lens. Ifthe focal length of the lens is 0.040 cm, howfar from the lens is the image?

6. Where is the object placed if a convex lenswith a focal length of 10.00 cm produces avirtual image 4.00 cm from the lens?

Lens Type Focal Point Distance toObject

Distance to Image

Convex positive positive positive or negativedepending on objectlocation

Images Formed by Convex Lenses

Example Problem 12.3A convex lens of a magnifying glassis held 3.00 cm above a page tomagnify the print. If the imageproduced by the lens is 4.20 cmaway and virtual, what is the focallength of the magnifying glass?

GivenDistance of the object from the lens, do = 3.00 cmDistance of the virtual image fromthe lens, di = –4.20 cm

RequiredFocal length of the lens, f

Analysis and SolutionThe correct equation is

= +

Substitute the values and their units,and solve the problem

= ( + )

=

Take the reciprocal of both sides.f = 10.5 cm

ParaphraseThe focal length is about 10.50 cm.

0.09524cm

1f

1cm

1–4.20

13.00

1f

1di

1do

1f


52

Lab: Images Produced by Converging Lenses Submission & Evaluation: Each student will submit a formal lab report. The formal lab report rubric for this lab is at the end of this document.

The report should be clearly organized and include: Purpose Hypothesis Materials Procedure

Observation Table Analysis

Discussion/Conclusion Extension

Refer to the Nelson Skills Handbook posted on ANGEL, p.601, 611-‐617

Purpose: The purpose of this investigation is to determine the relationship between the focal length, the image distance and the object distance of a converging lens. In this lab you will be investigating 5 cases in which the resulting image will differ based upon the location of the object with respect to the lens:

§ Case 1: the object is located beyond 2f § Case 2: the object is located at 2f § Case 3: the object is located between 2f and the focal point (f) § Case 4: the object is located at the focal point (f) § Case 5: the object is located in front of the focal point (f)

Hypothesis: Make a statement in response to the purpose. It should clearly conjecture an outcome that covers every case and is testable. It should address all the LOST characteristics. It should be in the form “As the object moves closer to the lens, the image __________________________________________________________________________________________________________________________________________________________________________________.” Materials: § Record a detailed list of all materials you use in this lab. Be specific. For example, instead of saying

“track” you could say “1 m long track”. Safety Considerations: § Watch when moving equipment that you don’t tip the track off the desk or accidentally hit another

student. Remember Sign Conventions: § Object and image distances are measured from the optical centre of the lens. § Object distances are positive if they are on the same side of the lens from which the light is coming;

otherwise they are negative. § Image distances are positive if they are on the opposite side of the lens from which the light is coming;

if on the same side, the image distance is negative. (Image distance is positive for real images and negative for virtual images)

§ Object heights and image heights are positive when measured upward and negative when measured downward from the principal axis


53

Procedure: § You must come up with the procedure for this lab and record it in your lab report. Remember,

procedure steps should be simple, present-‐tense, actions that another student could complete in order to get your same results. The first couple have been completed for you below. You still need to include them in your lab report.

1. Determine the focal length of your converging lens. Set your ray box to send out a wide beam of light and hold it about a metre away from your lens. Use your screen to locate the point on the opposite side of the lens where the light is focused to a point.

Measure the distance between the screen and the lens:

f = ______

2. Turn the lens around and repeat step 1 (to verify your measurement) f = ______

3. Calculate an average of both f measurements. favg= ______ 4. Using this average value, calculate the following object distances and record them in the attached

table: 2.5f = ___ 2.0f = ___ 1.5f = ___ f = ___ 0.5f = ___

5. Start adding your own steps here. Observations: Complete the observation table below and perform relevant calculation. Remember sign conventions! Case Object

Distance (do), cm

L (di), cm

O S (hi), cm

T 1/ do 1/ di 1/ do + 1/ di

1/f

1 2.5f = ___

2 2.0f = ___

3 1.5f = ___

4 f = ___

5 0.5f = ___

Show sample calculations in your lab report. Analysis: 1. As the object moves closer the lens what regular changes occur:

§ to the size of the image?

§ to the distance of the image?

§ to the attitude of the image?

2. At what object distance was it difficult, if not impossible, to locate a clearly focused image?


54

3. Where would you place an object in relation to the principal focus to form a: § real image? § virtual image?

4. How does the value of 1/f relate to the value of (1/ do + 1/ di ) for the cases involving real images?

5. How does the value of 1/f relate to the value of (1/ do + 1/ di ) for the cases involving virtual images?

6. Calculate the theoretical di for each case and find your percent error. Discussion/Conclusion: 1. Why does the method in step 1 work for finding the focal length of the lens? (hint – check out the rules

for rays in a converging lens and draw a ray diagram to help you explain your reasoning)

2. The thin-‐lens equation is io ddf111 += . Has your experiment confirmed or contradicted this

relationship? 3. Can you provide some suggestions on how to increase the accuracy of the experiment? (Consider parts

that you found difficult)

4. Based on your investigation and findings – what is the relationship among the focal length, the image distance and the object distance of a converging lens?

Extension: Match the following real-‐world device listed below to the characteristics you observed in your 5 object/image orientations.

Device Image Location and Attitude

Object Distance (In terms of f )

Photocopier (Image is the same size, and real)

Hand Magnifier (image is larger and virtual)

Overhead Projector (image is larger and real)

35 mm Camera (image is smaller and real)

Spotlight (parallel light – there is no image)


55

Category Level 4 Level 3 Level 2 Level 1 Below Level 1

Knowledge Understanding Concepts and Terminology. Overall lab submission demonstrates thorough and insightful understanding of concepts related to refraction.

No submission or below Level 1 expectation.

Thinking Hypothesis clearly conjectures the relationship between variables that covers every case listed in Purpose.


Procedure steps logical and reasonable. They could be easily followed by another person.

No submission or below level 1 expectation.

Observation table is complete and correct with sample calculations shown.


All 6 Analysis questions are complete and correct, with thorough supporting evidence.


All 4 Discussion answers are thorough, logical, complete and correct.


Communication All required elements are present and additional elements that add to the report (e.g., thoughtful comments, graphics) have been added and the report is on time.


Lab is well organized using the proper format, relevant vocabulary, mathematical conventions and units.


Application Extends refraction of converging lenses to real-‐life applications. Complete and correct for all 5.



56

Optics Review Practice Problems

Fill in the blanks to complete the statements. 4. List all of the possible characteristics of an image:

a. Location: The distance from the mirror can be _______________ than, _______________ than, or

the _______________ as the distance from the object to the mirror.

b. Orientation: The image can be either ____________________ or ____________________.

c. Size: The image can be _______________ than, _______________ than, or the _______________

size as the object.

d. Type: The image can be either ____________________ or ____________________.

5. Fill in the blanks to complete these definitions for reflections in a plane mirror.

a. The object distance is the distance between the _________________ and the _________________.

b. The image distance is the distance between the _________________ and the _________________.

6. The three rays from a point on an object that are particularly useful for locating the image of the point are a. the ray that starts ____________________ to the principal axis of the mirror, reflects, and then

passes through the _______________ _______________ of the mirror

b. the ray that passes through the _______________ _______________ and then _______________

from the mirror, travelling parallel to the ________________________ _______________

c. the ray that travels straight from the object to the __________________ of __________________

of the mirror

7. a. A positive image distance indicates that the image is ________________________.

b. A negative image distance indicates that the image is ________________________.

8. a. In a real image, the rays actually _______________, and the image would _______________ on a screen placed at the location of the image.

b. In a virtual image, the rays do _______________ actually meet, and _______________ image will appear on a screen placed at the location of the image.

9. When the centre of curvature of a concave mirror is between an object and the mirror, the image of

the object is __________________, __________________, __________________ than the object,

and located __________________ to the mirror than the object.

10. A concave mirror curves ____________ the object, while a convex mirror curves ____________


57

from the object. The focal point and the centre of curvature of a concave mirror are in ____________

of the mirror, while the focal point and the centre of curvature of a convex mirror are ____________

the mirror.

11. The value of the focal length of a convex mirror is negative because the focal point is ____________

_____ __________________.

12. An object in front of a concave mirror can be between the mirror and the ___________ __________,

between the focal point and the centre of _______________________, or beyond the ___________

of ______________________. However, a convex mirror is always between the _____________ and

both the centre of curvature and focal point.

13. Convex mirrors are often used as security mirrors in convenience stores. These mirrors reflect an

image of a ________________ ______________.

14. Images in spherical mirrors—either convex or concave—are distorted because of _______________

_______________.

Complete questions 15-‐27. Use full sentences where appropriate and show all work. 15.a. What is the range of wavelengths for visible light?

______________________________________________________________________________

b. Is any other part of the electromagnetic spectrum visible to the human eye? ______________________________________________________________________________

16. For each of the following wavelengths, list the corresponding type of electromagnetic radiation. a. 10 m _________________________________________________________________________

b. 1 mm _________________________________________________________________________

c. 10–9 m ________________________________________________________________________

d. less than 10–12 m ________________________________________________________________

18. a. What is the measure of the angle of incidence of an incident ray that is normal to a mirror? ______________________________________________________________________________

b. What is the measure of the angle of reflection for this ray? ______________________________________________________________________________

c. Is there any other angle of incidence for which the incident ray and the reflected ray will coincide?

______________________________________________________________________________


58

19. Draw two rays to determine the location of the image of point A in this diagram.

20. a. Locate the image of the triangle in this diagram. b. List the four characteristics of this image. c. How many rays do you need to draw to determine the image of the whole triangle? d. How many rays would you need to draw to determine the complete image of a rectangle?

21. Mark and label the focal point and the centre of curvature of the mirror in this diagram.

22. a. What is the orientation of the image when an object is located between a concave mirror and its focal point?

_______________________________________________________________________________

b. What is the orientation of the image when an object is located between the focal point and the centre of curvature of a concave mirror? _______________________________________________________________________________

c. Is it possible for the image to be upright when an object is 30 cm away from a concave mirror with a focal length of 25 cm? Explain your reasoning.

_______________________________________________________________________________

_______________________________________________________________________________

23. a. Label the diagram below with the following dimensions: f = 5 cm, do = 4 cm, and ho = 3 cm. b. Draw a ray diagram to locate the image. c. Determine the scale of the diagram and measure the image height and location.

Location: ____________________________

Orientation: __________________________

Size: ________________________________

Type: _______________________________


59

24. A concave mirror has a focal length of 5 cm. An object 2 cm high is 11 cm from the mirror. Complete the ray diagram and measure the image height and image distance.

25. Draw a ray diagram for the convex mirror in this diagram.

26. Some vehicles have a two-part side mirror that has a plane mirror with a smaller convex mirror on top of it. a. What is the advantage of the plane mirror?

______________________________________________________________________________

______________________________________________________________________________

b. What is the advantage of the convex mirror?

______________________________________________________________________________

______________________________________________________________________________

27. A concave mirror has a focal length of –5 cm. An object with a height of 4 cm is 3 cm from the mirror. Complete the ray diagram below, and use it to measure the image height and distance.


60

1. Calculate the refractive index for a substance if the speed of light in that medium is:

a) 2.6 X 108 m/s (n=1.15 ) b) 1.2 X 108 m/s (n= 2.5) c) 0.48c (n = 2.08)

2. Calculate the angle of refraction for light as it passes from benzene (n = 1.5) to each of the following media, at an angle of incidence of 45°:

a) Ice (n = 1.30) (θR=55°) b) Water (n = 1.33) (θR=53°) c) Flint glass (n = 1.91) (θR=34°)

3. Calculate the angle of incidence for an angle of refraction of 25° for:

a) Zircon (n = 1.90) to water (n=1.33). (θI=17°) b) Water (n=1.33) to ice (n=1.30). (θI=24°) c) Diamond (n = 2.42) to flint glass (n=1.91). (θI=19°)

4. Calculate the critical angle for: (see above for index of refractions!)

a) Zircon to water. (θCRITICAL=44°) b) Diamond to ice. (θCRITICAL=32°)

c) water to ice. (θCRITICAL=78°) 5. A ray of light passes from kerosene to glass (n=1.91). The angle of incidence of the light

is 45.2o and index of refraction for kerosene is 1.08. Calculate the angle of refraction in the glass. (41o)

6. A ray of light passes from air into a glass prism at an angle of incidence of 35o. If the angle of refraction in the glass is 23.7o, what is the speed of the light in the glass? (2.1 x 108 m/s)

7. The critical angle for diamond is 24o. Determine the index of refraction of diamond. (assume it goes from diamond to air) (2.46)

8. Describe an application of total internal reflection used in the communications industry. 9. Provide a brief explanation for the following concepts that relate to refraction. Make sure to include a diagram of your own or from the internet for each concept.

a) Mirages b) Apparent depth c) The flattened sun d) The rainbow

SNC2D Physics – Light and Optics Optics Learning … or FALSE: RED light has a shorter wavelength...

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Transcript of SNC2D Physics – Light and Optics Optics Learning … or FALSE: RED light has a shorter wavelength...