I like the cheese/chocolate in the Microwave trick.
@sophiecentaur
yep I get that a reflective surface "can" bound a standing wave (and I have no interest in any super weapons :-) ), but I thought that an electromagnetic wave was pretty much the only wave I knew of that didn't require any...
This might help too ... (from
http://www.osha.gov/SLTC/radiofrequencyradiation/electromagnetic_fieldmemo/electromagnetic.html#section_3 )
Pd = E x H
Watts/meter2 = Volts/meter x Amperes/meter
where
Pd = the power density,
E = the electric field strength in volts per meter...
A standing wave can be produced in a guitar string where the wavelength of the wave is the same length as the string (I believe this is referred to as the first harmonic) and where the string is an exact multiple of the wavelength of the wave (referred to as the second and subsequent harmonics)...