Energy of Light

1. Do you think light has energy? How do you know?
2. If light does have energy, does all light have the same amount of energy? How do you know? (Think back to other experiments we have done to use as evidence for your answers.)

(Day before) Bring any glow-in-the-dark clothes/objects/materials from home to use in our experiment!

Get the phosphorescent paper, LED lights, and a button battery from your teacher.

Dim the lights in your classroom and make it as dark as you can. Notice the eerie green glow coming from the phosphorescent (glow-in-the-dark) paper. Why do you think it is glowing? Where did the energy come from to produce the glow?

Now get out the red and blue lights and experiment with drawing and writing messages on the paper. Observe how the brightness of your messages changes with time, and discuss your observations of the effects of the different lights with a partner.

Another interesting thing: If you shine the red light on a bright spot on the paper, you may find that the spot actually gets dimmer. If the paper is warm, it glows more brightly. This means the energy is used up faster. Shining the red light on the paper can warm it up right where the red light hits; this will make the surface discharge faster, leaving a dark spot!

What can you say about the energy of red light compared to blue light?

Using colored pencils/markers, draw what you think the transverse waves for these two colors of light look like.

Bonus: Draw a physics model of what you think is happening inside the phosphorescent paper when it is hit with red light or blue light.

In your Discussion Diamond groups, answer the following questions:

1. What can you infer about the energy of other colors of light?
2. What would happen if you shine a yellow light on the phosphorescent paper?
3. Purple light?
4. Orange light?
5. Radio waves?
6. X-rays?

It might be helpful to look at a picture of the electromagnetic spectrum while answering these questions.