Energy Changes: Lesson 2 Properties of Light

Essential Question How do I see light and colors?

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.

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

Video Clip – What Is Light?

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.

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.

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

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

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.

Waves Video – Bill Nye

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.

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.

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

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

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

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