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Re: [Phys-l] Microwave oven experiment

Craft, Peter wrote:
Several staff at our school have just conducted an experiment to measure the velocity of microwaves using a domestic microwave oven. They followed the well known method of placing chocolate in a tray and running the microwave until spots appear in the chocolate where the anitnodes occur in the standing waves. These should occur at 1/2 lambda or around 6-6.5 cm to give the "desired" velocity. In both cases the hot spots were well defined at 11.5cm or 1 complete wavelength. The microwave oven states that it operates with a frequency of 2450 Hz.
Could anyone advise us if we are making an error or explain why we are not getting the expected results.

Thanks

Peter Craft
I suggest that identifying microwave hot spots as antinodes may be the issue.
If you place a loudspeaker in a room with hard walls, floor and ceiling, there will be intensity peaks at particular spots. It would be unwise to identify these locations only with the sound wavelengths in use. Details of room structure would reposition these hot spots, after all.

Brian W