ISEN-ASTC-L is a service of the Association of Science-Technology Centers Incorporated, a worldwide network of science museums and related institutions. ***************************************************************************** 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 *********************************************************************** More information about the Informal Science Education Network and the Association of Science-Technology Centers may be found at http://www.astc.org. To remove your e-mail address from the ISEN-ASTC-L list, send the message SIGNOFF ISEN-ASTC-L in the BODY of a message to [log in to unmask] *********************************************************************** More information about the Informal Science Education Network and the Association of Science-Technology Centers may be found at http://www.astc.org. To remove your e-mail address from the ISEN-ASTC-L list, send the message SIGNOFF ISEN-ASTC-L in the BODY of a message to [log in to unmask]