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Narrator: For this activity, I'm going to walk you through how to turn a paper towel
tube into a spectroscope. You will need a paper towel tube,
two roughly square pieces of aluminum foil, two strips of aluminum foil,
a piece of diffraction grating, a pair of scissors, and some tape.
We will start by constructing the end that goes up to your eye.
For this end, you will need one of the aluminum foil squares.
Fold it into quarters and cut of the corner where all the folds meet. This gives us
the hole in the middle of the piece of foil when everything is unfolded. The diffraction
grating, which looks like a piece of clear plastic with a rainbow sheen to it,
is going to be taped over this hole, so the hole should be just a little bit smaller than the
piece of diffraction grating. Be very careful to touch the diffraction grating
as little as possible so you don't leave fingerprints on it. Tape the edges so that you're
still able to see through the grating. Take the
whole foil square and wrap it around one end of the paper towel tube so the piece of diffraction
grating is centered over the tube end. It is more structurally stable if you
put the tape on the inside. You can tape this into place immediately.
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Next we will construct the other end of the spectroscope. Take the other
aluminum foil square and cut a hole in the center of it in the same way as before.
Now take each of the strips of aluminum foil,
and fold them lengthwise, taking care to give them a nice, sharp crease.
Place them over the foil square, with the creased edges facing each other to
create an open slit. The size of the slit should be about the thickness of a coin.
Tape the two strips in place, keeping them nice and parallel.
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This foil square can now wrapped around the other end of the paper towel tube in the same
way as before, but this time, do not tape it into place right away.
When you look into your spectroscope, remember that it's the diffraction grating
end that goes up to your eye. When you point your spectroscope at a light source
you should be able to see a spectrum on the walls of the tube. While looking at a light
source that produces a spectrum, rather than a continuous rainbow,
rotate the slit end, which you have left untaped. You should see the
spectrum change shape, going from a long, thin smear of color to a broad spectrum
with clear lines in it, and back again. Find the point where the spectrum is as
thick as you can make it, and all of the individual lines are clear and straight.
When you have found this point, you can tape the slit end in place.
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