Energy UnitWeek 34

Directions1.Prepare your desk for science.• Science notebook

2.Use voice level 0 (no voice) to review your light energy notes from notebook pg. 83.

Targets & Warm Up

Targets:• Students will understand how light can

be reflected, absorbed, or refracted.

Warm Up: How does light travel?

How does light travel?

Light travels in straight lines called __________ that fan outward from the source of light.

BUT

Light can change when it strikes (hits) an object.• Reflect• Absorb• Refract

rays

Table of Contents

Date Title Page5-19-15 Behavior of Light 84

Once you are finished with the Table of Contents, go to page 84 and add the title and date to the top of the page.

Reflection

• Occurs when light waves bounce, or reflect, from a surface back to our eyes

• Some objects reflect more light rays than others

Absorption

• Occurs when an object takes in the light wave• After a light wave is absorbed, it becomes a

form of heat energy

Color and Light• We see colors because objects reflect and

absorb light.• An object is a certain color because it absorbs

all colors except for the color that it reflects back to our eyes.

Color and Light

Reflect? Absorb?

Color & LightWhat color is reflected? What color(s) are absorbed?

Reflected: RedAbsorbed: All other colors

Reflected: NoneAbsorbed: All colors

Reflected: All colorsAbsorbed: None

Letting Light Through (Transmission)

• Transparent: Let most light rays pass

• Translucent: let some light rays pass

• Opaque: Do not let any light rays pass

How Light Changes Direction

• Light travels fastest through outer space where there is no matter

• Light slows as it travels through various mediums– Travels slowly in a gas– Travels more slowly in a liquid

• When light moves at an angle from one medium to another, some light…– Is reflected or absorbed– Passes through and changes directions (bends)

Refraction

• The bending of light caused by the change of speed that occurs when the wave passes from one medium into another

Light travels from the pencil through water, though a glass, and through the air to your eye

Refraction

Lenses

• Lenses are curved pieces of clear glass or plastic that refract light that passes through them

• Two types:– Concave– Convex

Convex Lens

• Thicker in the middle than at the edges

• Light rays bend in toward the middle of the lens

• Makes things appear larger

• Found in magnifying glasses and microscopes

Concave Lens

• Thinner in the middle than at the edges

• Light rays bend out and spread apart

• Makes things appear smaller

TelescopesConcave and convex lenses are often used together to make details look sharper

StudyJams Video

Light absorption, reflection, and refraction

http://studyjams.scholastic.com/studyjams/jams/science/energy-light-sound/light-absorb-reflect-

refract.htm

Extra Time?

Pretend that you are shining a flashlight on these objects. Do the objects reflect, absorb, or refract light?

Reflection Questions

• What is reflection? What is absorption? What is refraction?

• What are some examples of when light is reflected, absorbed, or refracted?

Homework

Targets (Revisited)

• Students will understand how light can be reflected, absorbed, or refracted.

Homework

Subject Homework Due DateScience Light Energy worksheet Wednesday

(tomorrow)