3Chapter 4Sound &

Light

SoundSound travels from one place to

another as sound wavesA sound wave is a

longitudinal wave that can only travel through matter (Solids, liquids, gases)

Vibrations produce sound waves by moving molecules in air.

How does the ear work?

Sound Waves

Sound waves are sent. The outer ear “catches the sound waves”. The middle ear takes the sound waves and

“vibrates” the eardrum. The inner ear sends the messages to the

brain.Middle Ear

Inner Ear

The brain puts it together and hooray! You hear your favorite song on the radio.

Outer Ear

How sound waves travel!

Outer ear – Catches sound waves

Middle ear – Vibrates

EarDrum

Inner ear – Sends

MessageTo

Brain

Sound waves are made up of two parts: 1. Rarefactions

2. Compressions The tuning fork causes molecules

in the air to move closer and then farther apart

Like other waves, a sound wave can be described by its: 1. Wavelength

2. FrequencyWavelength:

rarefaction to next rarefaction (vice versa)Frequency:

a given point in one second

distance from center of

The # of wavelengths that pass

The unit for frequency is

Hertz (Hz)

A sound wave’s speed increases when

Solids and liquids are dense than gases.

Speeds of Sound Waves

the material’s density increases.more

Sound waves usually travel faster in than in orsolids liquids gases.

The speed of sound waves increase as the temperature increases.

If sound travels faster in water than in air…then why is it harder to talk to someone underwater?

• Sound couples poorly moving from air to water.

• Your lungs provide the burst of air when talking underwater.

• In order for someone underwater to hear you, the sound waves have to go from the air in your mouth to the water surrounding you.

• This causes the sound waves to get reflected where the air meets the water.

Pitch:

A sound wave with a higher frequency has a pitch.

Pitchhow high or low a sound seems

higher

A sound wave with a lower frequency has a pitch.lower

Loudness is the human sensation of

A shout carries more than a whisper.

Loudness

energy

The energy that the wave carries relates to its

how much energy a sound wave carries

amplitude.

The more energy a wave has the

A is one way to compare the loudness of sounds

Loudness (cont’d)

decibel scale

greater the amplitude.

An echo is a

Echoreflected sound wave.

Some animals useto locate

their prey and detect objects.

Animals such as dolphins and bats send out and when those waves hit

an object it bounces back

echolocation

sound waves

vibrations.

Sound Travels Through Matter

GasesMost of the sounds we hear travel through gases, such as air.

Sound waves travel slowly through the air.

For example: Sound from a bell, a horn, or an alarm clock travels through the air.

LiquidsSome sounds that we hear travel through water.

Sound waves travel faster through water than through the air.

Sonar is the way to use sounds to locate objects under water.

SolidsSome sounds that we hear travel through solids.

Sound waves travel very fast through solids.

For example: When you hit a drum, it vibrates, then the sound travels through the air, to your ears.

Ultrasound

• Ultrasound scanners convert high-frequency sound waves to images of internal body parts.

• The sound waves reflect from structures within the body.

• The scanner analyzed the reflected waves and produces images called sonograms.

Breaking the Sound Barrier

• When the vehicle (jet) exceeds the speed at which sound travels.

• The cone of vapor you see is the existing moisture in the air being condensed by pressure wave created by the vehicle creating a cloud.

Lesson 2: Light

Light is a type of wave called an

Light

electromagnetic wave.Light does not need a to

travel through.A medium is

Light can travel through aAn example of a vacuum is the

medium

a material through which a wave travels.

vacuum.

space between Earth and the Sun.

Light travels at different speeds through different mediums

The electromagnetic spectrum includes

Wavelengths are measured in

Electromagnetic Spectrum

a range of electromagnetic waves.

nanometers.

Wavelength is 400nm Wavelength is 700nm

A is something that emits (gives off) heat.

Examples of light sources include:

A light ray is a

light source

burning candle, sun, light bulb

narrow beam of light thattravels in a straight line.

Laser

We see things because they light into

Homework

reflectour eyes.

A is the process of light striking an object and bouncing off.

reflection

Depending on how materials interact with light, they are classified as: transparent, translucent, or opaque

Transparent: almost all light passes through

object

Translucent:most light passes through & blurry image forms

Opaque:no light passes through it

When light waves interact with matter they can be:

1. Transmitted

2. Absorbed

3. Reflected

light waves travel through a material

(transparent object)

light waves are converted to other forms; translucent object

light waves bounce of surface of material

(opaque object)

Law of Reflection

Incident ray Reflected ray

Angle of incidence

Angle of reflection

Mirror

The angle of incidence is always equal to the angle of reflection.

Normal

This is an example of scattering.

HAVE YOU EVER SEEN DUST PARTICLES FLOATING IN THE AIR WHEN A BEAM OF SUNLIGHT SHINES THROUGH A WINDOW?

Scattering occurs when light waves travelling in one direction are made to travel in many directions.

Light waves change when they travel from one material to another.

The bending of a wave as it moves from one material to another is called

This is due to a change in

Refractiondirection

refraction.

speed.

Light is slower when passing through Light

dense materials.

Retina

Rods • 120 million• Allow you to see in dim

light• Black and white signals

– does not allow you to see color.

Cones• 6 million• Response to light waves with

different wavelengths allow you to see different colors.

• 3 types – each detecting a different wavelength.

• In some people, not all 3 function properly = color blindness/color deficiency.

People with color deficiency cannot see a number in this picture!

How your eye works

LESSON 3:MIRRORS & LENSES

Light waves reflect off aThe reflects light rays traveling in the same direction at the same angle.

mirrorlike surface.

smooth surface

Regular Reflection

When a surface is not smooth the reflected angle travels in many different

Diffuse Reflection

directions.

MirrorsA is any reflecting surface that forms an image by regular reflection.

mirror

Plane Mirror:Flat surfaceSame image, just

reversed left to right

Concave Mirror:Curved InwardObjects can appear

upside down or right-side up

Convex Mirror:Curved outwardObjects are smaller

and right-side up

Cosmetic mirrors are often concave mirrors.

Image becomes magnified.

Convex mirrors are often used for safety purposes.

A lens is a

Convex Lenses

transparent object with at least

• Curved outward• Thicker in the middle• Objects appear larger

Lens

one curved side that causes light to change direction

• Curved inward• Thicker at the sides• Object is shown smaller

Concave Lens

Glasses for nearsightedness (can’t see far)

How do objects get their color?Objects light.Colors depend on the of the light waves it reflects.

reflectwavelengths

The rose looks red because all the other wavelengths are absorbed but red is reflected.

White light is a combination of all light waves.

Neon lights emit different colors.(give off)

The appearance of an object changes under different lights.