1. Energy Changes: Lesson 2 Properties of Light

2. Essential Question
How do I see light and colors?

3. How many sources of light can you list and explain?
In your groups, discuss all of the sources of light that you can think of and list them on the white board.

4. Did You List Any of These Sources of Light? Do You Have More?
Sun
Fire
Lightning
Firefly
Flashlight
Light bulb
Laser beams
Traffic Lights

5. Video Clip – What Is Light?

6. Properties of Light
Light is a form of energy that you can see when it interacts with matter.
Light travels in waves.
Waves carry energy.

7. You Can Make A Wave
You can make a wave by tying one end of a rope to a doorknob and shaking the other end up and down.
The energy moves through the rope from your hand to the doorknob. The wave appears as a series of high points and low points in the rope.

8. Crests Troughs A high point of a wave is called a crest.
A low point of a wave is called a trough.

9. Wavelength Halfway between a crest and a trough is the resting point.
The wavelength is the distance between one crest or trough and the next.
Rest

10. Amplitude
The amplitude is the distance between the resting point and a crest or trough.
Rest Position
You can think of wavelength as the length of a wave and amplitude as the height.

11. Waves Video – Bill Nye

12. Part 1 – Properties of Light
Light travels in straight lines in all directions from a light source:
Laser
A light source may be a light bulb, a fire, or the Sun.

13. Light Waves
Light waves travel until they strike an object.
If the light waves can’t pass through the object, a shadow forms behind the object.

14. Shadows
A shadow is an area that is dark because light does not reach it.
Shadows form because an object blocks the light.
Shadows are places where light is “blocked”
Rays of light

15. Light travels much faster than sound.
For example:
Thunder and lightning start at the same time, but we will see the lightning first.

16. We see things because they reflect light into our eyes:
Homework

17. Properties of Light Summary
Light travels in straight lines
Light travels much faster than sound
We see things because they reflect light into our eyes
Shadows are formed when light is blocked by an object