Physics

9th - 12th grade

30 minutes

Law of Refraction

The students will learn what determines the color of light and why passing "white light" through a prism produces a visible spectrum of the colors.

1. For the students to understand what property of light determines its color.
2. For the students to gain a basic understanding of why a prism creates a visible spectrum.

• Prism
• White light source
• Laser

Procedure

Opener

Likely all students at this age have seen a prism before and know what happens when light passes through it. But does it make a difference what type of light is used?

Show the students a prism, and use a white light source to produce the resulting color spectrum they've all come to expect. Now bring out a monochromatic light source, such as a laser, and ask the students what they expect to happen if this light is passed through the prism? Will it still produce the spectrum? Why or why not?

Development

This powerpoint discusses the origin of color and the differences between white light and laser light, working through a thought process to help the students explain how different colors might be separated when passing through a prism. It goes onto introduce the concept of dispersion.

Here's a website with a nice discussion of rainbows.

http://rst.gsfc.nasa.gov/Intro/Part2_4.html