Make a Spectroscope

This lesson developed by Reach Out!
Recommended Age: Later Elementary

What You Need

  1. Paper towel tube
  2. Aluminum foil
  3. One edged razor blade (use with an adult!)
  4. Rubber band
  5. Diffraction grating mounted in a square piece of cardboard (You have to buy these from a hobby or science store)
  6. Glue
  7. Lamp with removeable shade or a candle
  8. Tape

What You Do

  1. First, glue the diffraction grating to one end of the paper towel tube.

  2. Take a small piece of aluminum foil and mold or cover up the other end of the tube. Don't glue it down as you will be moving the foil around the end of the tube in the experiment.

  3. With the blade, carefully make a narrow slit in the middle of the piece of aluminum foil. YOu have made a simple spectroscope!

  4. Turn on the lamp and remove the shade. Or, carefully light a candle.

  5. Hold your spectroscope so the slit in the foil is close to the light source.

  6. Look at the light through the diffraction grating. Turn the aluminum foil a little bit until you see what looks like a rainbow.

    What Is Happening

    We look at light from a light bulb or candle and we assume the light is white. But it really isn't! White light is really made up of many colors that our human eyes just don't detect or see by themselves. Most will see seven colors through their spectroscope- violet, indigo, blue, green, yellow, orange, and red.

    The diffraction grating has tons of little skinny lines drawn on it. These little lines pick up and break the white light into the many colors of the spectrum.