That is a nifty little trick! 6cm seems like a damn long wavelength, though when all I study in physics are light waves in the 10^-7 spectrum. posted by jmd82 at 10:54 AM on April 30, 2004
But he doesn't say anything about the student assessment. The lesson is useless unless you can measure achievement. I bet this teacher got fired. posted by MetalDog at 12:36 PM on April 30, 2004
you can also (i've seen his done, although it sounds terribly dangerous) put a normal lightbulb in a cub, metal cap down, with water covering the cap (to stop arcing). place it on the turntable and turn the microwave on - the light glows more and less brightly as it moves from nodes to antinodes in the standing wav pattern. posted by andrew cooke at 12:56 PM on April 30, 2004
Can somebody give me a simple explanation of why the distance between the spots = 1/2 the wavelength? I understand it has to do with waves re-inforcing and cancelling out, but why 1/2? posted by signal at 1:05 PM on April 30, 2004
Another cool one I did in High School was take a 10 foot pipe that was about half a foot in diameter. Drills holes a few centemeters apart. On one end, attatch a speaker (be sure its sealed) and on the other end, hook up the Bunson Burner- once again ensuring its sealed. Turn on the burner and the music, put a match to one of the holes, and you got a sinutoital wave of fire. posted by jmd82 at 1:52 PM on April 30, 2004
signal: a standing sine wave is not a stationary wave, but rather a pattern of alternating nodes, which stand still, and antinodes, which alternate from high to low displacement.
Microwave ovens are sized to create standing waves, and the antinodes are where the heat is generated. Since there are two antinodes in each wavelength - one high and one low at any given time - the hot spots are 1/2 the wavelength apart. posted by nicwolff at 3:40 PM on April 30, 2004
This image from the linked article tells the whole story so I'll just drop it in here:
¡°Why?¡± asked Larry, in his practical way. "Sergeant," admonished the Lieutenant, "you mustn't use such language to your men." "Yes," accorded Shorty; "we'll git some rations from camp by this evenin'. Cap will look out for that. Meanwhile, I'll take out two or three o' the boys on a scout into the country, to see if we can't pick up something to eat." Marvor, however, didn't seem satisfied. "The masters always speak truth," he said. "Is this what you tell me?" MRS. B.: Why are they let, then? My song is short. I am near the dead. So Albert's letter remained unanswered¡ªCaro felt that Reuben was unjust. She had grown very critical of him lately, and a smarting dislike coloured her [Pg 337]judgments. After all, it was he who had driven everybody to whatever it was that had disgraced him. He was to blame for Robert's theft, for Albert's treachery, for Richard's base dependence on the Bardons, for George's death, for Benjamin's disappearance, for Tilly's marriage, for Rose's elopement¡ªit was a heavy load, but Caro put the whole of it on Reuben's shoulders, and added, moreover, the tragedy of her own warped life. He was a tyrant, who sucked his children's blood, and cursed them when they succeeded in breaking free. "Tell my lord," said Calverley, "I will attend him instantly." HoME²Ô¾®¿Õ·¬ºÅѸÀ×Á´½Ó
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posted by me3dia at 9:14 AM on April 30, 2004