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Dear microwave folks,
I can't help but think of the very dangerous and wonderful demo a
physicist taught me in which you can generate a ball of plasma in the
microwave. I've never seen anything as bright, nor heard the microwave
sing at 120 Hz so loudly, nor have I ever felt so acutely the prospect
of death by microwave. A very popular party trick at my house.
For those interested, the experiment requires:
1 pyrex 2-cup measuring cup (please use pyrex not other glass!)
3 spacers (I've used plastic tops to spice containers)
A candle with some charred toothpicks or matches on top (votives work
fine)
You put the candle in the middle of the microwave facing up. Arrange
the three spacers around the candle such that you will be able to perch
the pyrex cup, upside down, on the spacers around the candle. Light the
candle, flip the pyrex over the candle on the spacers, shut the door,
and let her rip!
You will see some sparks of light, and then a pinkish-blue light will
emanate from the microwave as if some small physics god were erupting
into life in your kitchen. You will also hear a very loud buzzing,
which, we were glad to discover the first time we tried this, is not the
sound of your microwave about to kill you. After a couple seconds, shut
off the microwave. Wait to touch the pyrex--it is very hot and the only
real danger in this experiment is the potential to burn yourself. The
glass may also explode; be careful.
I found an explanation for this, along with some other wild microwave
tricks, here-- http://www.amasci.com/weird/microexp.html#exper.
Happy plasmaing!
Nina Simon
International Spy Museum
-----Original Message-----
From: Informal Science Education Network
[mailto:[log in to unmask]] On Behalf Of Sandy Eix
Sent: Wednesday, October 26, 2005 11:38 AM
To: [log in to unmask]
Subject: measuring the speed of light in a microwave
ISEN-ASTC-L is a service of the Association of Science-Technology
Centers
Incorporated, a worldwide network of science museums and related
institutions.
************************************************************************
*****
Hello clever and creative folks.
Have any of you ever tried to "measure" the speed of light with a
microwave? The idea goes like this: you put a layer of melty food
(chocolate chips or processed cheese slices) in the microwave on a plate
or tray, which you cleverly position so that the turntable doesn't turn
it around. You zap it for about 20 seconds, or until isolated spots
start to melt. The melted bits represent antinodes of the standing waves
in the oven. So, the distance between melted bits should be half the
wavelength of the microwaves. The frequency of the microwaves is printed
on the oven itself, usually 2450 MHz. wavelength x frequency = c.
Now, I've tried this with many different foodstuffs, at the bottom and
the middle of the several ovens, with and without a cup of water to
absorb microwaves, on low and high powers, and the closest I get to the
real value of c is still 25% off. In fact, I'm quite consistently 25%
high. And yes, I have double and triple checked the frequency.
I'd love to hear from anyone else who's tried this... or who would like
to try it and tell me what happens! If nothing else, you'll end up with
a lot of half-melted chocolate chips to share with your colleagues.
thanks,
sandy
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More information about the Informal Science Education Network and the
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To remove your e-mail address from the ISEN-ASTC-L list, send the
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