Fun With CDs

Fun With CDs ~15 Minutes

Description: Observing cool optical effects

Objective: To learn about colours and reflection

-describe properties of materials, including colour, shape, texture, size, and weight (grade K)
-explain properties of light (e.g., travels in a straight path, can be reflected) (grade 4)

Materials: One CD per group (per child is better), several desk lamps, pencil crayons.

Doing it:
A1. Find a desk lamp or other bright light. Stand with the lamp behind you (about 1 or 2 meters away)
A2.Hold the CD in front of your face, about 5-10 cm from your eye. Try to see the reflection of the light in the CD. It helps to close one eye.
A3.Try to make the reflection of the light go through the hole in the cd. You should see a beautiful circular rainbow (this may take a little patience). It may be easier to hold the cd with your finger through the hole.

Fig 1.1 - visual using fluorescent light instead of a desk lamp.
Fig 1.2 - visual using fluorescent light instead of a desk lamp.

Explanation: White light is made up of different colours of light. The CD acts like a prism (actually it is something called a diffraction grating) It separates the light into different colours.