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Rubberband Waves
This week's experiment is in response to a request that
I got from Wendy Sadler at the Techniquest in Wales. She wrote asking for
experiments that use rubber bands to use in an upcoming show. This is one of my
favorite science experiments with a rubberband. I don't give out e-mail
addresses, but if you have one that you like better, send it to me and I will
forward it on to her.
For this experiment, you will need:
Stretch the rubberband tightly and pluck it like a
guitar string. You will hear a sound and see the rubberband vibrate back and
forth. It vibrates so fast that it hides some of the details of what the
rubberband is doing. To get a different view, we need a different way to view
the vibrations. One way to see this sort of thing is with the use of a strobe
light. A strobe is a light that flashes on and off very quickly. One flash of
the light lets you see the object in one position. Then the light goes out.
When it flashes again, you see the object in another position. By flashing on
and off very quickly, a strobe can seem to freeze motion, making a vibrating
object seem to stand still or slow down. Now, if we only had a strobe light.
Well, we do have something that will serve the purpose. We will use the
television.
Sit where you normally do to watch television. Stretch
the rubber band again and hold it up between you and the television screen.
Pluck the rubberband and watch what happens. Waves! You will see them much
better when the screen is a light color, and you can change their appearance by
changing how tightly you stretch the rubberband.
How does the television change the way you see things?
While the screen seems to be on all the time, actually it is not. If you look
closely at the screen, you will see that it is made up of tiny dots. While
these dots seem to be lit all the time, they are actually flashing on and off,60
times per second. The flickering of the screen gives us just the strobe effect
that we need to see the details of the rubberband vibrating.
Of course, this experiment works best when you have the
right program on the television. I found that Fawlty Towers worked very well,
but it was hard to keep my attention on the rubberband while I was laughing.
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