How to See a Rainbow with a Home-made Spectroscope!

We all love to see a rainbow after it rains! A rainbow is a symbol of hope and promise of good things to come.

Rainbows are always made up of the same colors and in a certain order. First comes red, then orange, yellow, green, blue, indigo, and violet. A great way to remember the colors in order is by thinking of a name! Roy G. Biv 

You don’t have to wait for a rainstorm to see the colors of a rainbow! You can make your own spectroscope. What is a spectroscope? The word spectrum is a band of colors as seen in a rainbow, and scope is ‘to see’. So, put them together and a spectroscope is an instrument which allows you to see the colors that make up white light in the form of a rainbow.

Materials:

One paper towel tube

Paper or cardstock, tape

An X-Acto (or artist’s) knife (ask an adult to help with this!)

Markers

One CD disk

Procedure:

First, it is fun to color your paper towel tube. I used the colors of the rainbow, but you can use whatever colors you would like.

Ask an adult to cut a small square hole in the tube close to the bottom of the tube. This will be the hole you look through when finished.

Ask an adult to cut a slit at about a 45-degree angle on the opposite side from the hole.

Use the top of the tube to trace a circle on a piece of paper or cardstock and cut a rectangular hole in the middle of the circle.

Tape the circle to the top of the tube.

Take the CD disk and insert it into the slot with the shiny side up.

Spectroscope.jpg

spectroscope 2.jpg

OK, now for the fun part!

Go outside and hold your spectroscope in one hand while you close one eye and peek into the hole on the bottom of the tube.

Don’t look directly into the sun but stand in a sunny location. You may need to tilt your head up and down until the rainbow appears!

You can also do this with a bright overhead light in the house.

How does this work?

A CD has a mirrored surface with a spiral track running through it. The tracks are evenly spaced and diffract light.

Diffract means that the tracks bend the white light entering the tube into colors.

Because the surface of the CD is mirrored, the light is reflected to your eye and you see a small rainbow!