Why wait for a rainy day to see a rainbow? Build your own spectrometer and you’ll not only see a rainbow, but you’ll also find out how they’re made!
When the sun shines down on us, it sends every color together in what is known as white light. White light is made up of many colors with different wavelengths and frequencies, but unless they are separated, we can’t see them all. This is where the CD comes in. It may look and feel smooth, but it actually has tiny ridges where the light will diffract off of. Diffraction is the spreading and separation of light. Because the colors all have different frequencies, they will diffract at different angles and a rainbow will be seen!