### Directions

**Getting Ready**

If you wish to assign students a color, have several pieces of different colored construction paper ready for the students. The traditional colors of the rainbow (red, orange, yellow, green, blue, indigo, violet) work best.

- Tell the students they are going to pretend to be white light. Have the students stand in a straight line. Have them arrange themselves so they are in the same order as the colors of the rainbow (ROY G. BIV) based on the color of their shirt (if you have uniforms in your school or a poor variety of shirt colors present, you can give each student a sheet of colored construction paper and have them line up by the color of their paper).
- Tell the students that all colors of light travel at the same speed. Therefore, when they start walking, they all must walk at the same speed.
- Tell the students that light can be thought of as a wave and that different colors of light have different wavelengths. Therefore, they will all take different step lengths.
- Tell the students that the students representing blue light will take small steps since blue has a short wavelength. Students wearing green will take medium-sized steps and students wearing red will take long steps. Other colors should be adjusted accordingly.
- Have all the students walk toward you at the same speed. Tell them to observe the other “colors” as they walk. Tell them that white light is made up of all the colors, so they are pretending to be white light.
- Have the students return to the starting point. Stand 10 feet or so from the students. Tell them you are a filter and you are only going to let through a certain color of light (you might wish to choose the color that is most popular that day). Have the students walk toward you. Everyone who is not the same color as the filter has to stop when they reach you. Tell the students this is what a colored filter does. It stops all colors of light except one. NOTE: If you are, for example, a red filter and two students are wearing slightly different shades of red shirts, let them both pass. Tell the students that filters usually let though a small range of colors and not just one color.
- Now tell the students they are going to learn the difference between laser light and normal light. Tell the students that they will now all be the same color so they will take the same size steps and walk at the same speed. Have the students stand in a line and start walking toward you at the same speed taking the same size steps. Tell them not to worry about being in step with the person next to them. This exercise simulates monochromatic (single color) light that is not coherent.
- Next, tell the students to line up and walk toward you taking steps of the same size. This time, however, tell them they all have to be in step. Tell the students this simulates laser light and is called coherent. All the light is “in step.” Scientists would say the light has a constant phase relationship. In coherent light, all the individual photons act as one wave.