How to make a spectroscope

A spectroscope is a device that separates light into its individual colors in a rainbow-like band called a spectrum. The spectrum of each chemical element looks slightly different, so scientists use spectroscopes to see what elements make up the sun and stars. Try making your own spectroscope and turn any light in your house into a rainbow! What You Do: Line the inside of the cardboard tube with black construction paper.

Cut two circles out of the construction paper. Make them slightly bigger than the cardboard tube. In the middle of one of the circles, cut a square with sides about 1.5cm long. Tape the diffraction grating over the square hole, and then tape the circle over one end of the cardboard tube with the diffraction grating on the inside. The center of the other circle needs to have a very narrow slit for light to enter through. Since cutting this can be difficult, just make a rectangular hole about 2.5cm long.

Then tape two rectangles of black paper over the hole, leaving a narrow slit between them. It’s a good idea to cut your rectangles from the edge of the paper so you are sure to have straight edges to use for the sides of the slit. (The right-hand photo shows this step using a white circle so you can easily see how to line up the rectangles.) Hold the slotted circle over the other end of the cardboard tube and look through the grating end at a light source. You should see a color spectrum on the inner side of the tube.

(There might be one on either side of the slit.) It may be very narrow; turn the slotted circle until the spectrum widens out, and then tape the circle in place. You now have a working spectroscope! Use it to look at several different types of light: a normal incandescent light bulb, fluorescent light, LED light, a glow stick, even sunlight. (But be very careful – do NOT look directly at the sun through your spectroscope!) You can also look at the flame of a match or candle, if you have someone else hold it for you.