[Dennis ODonnell]

Dennis ODonnell  asked the Naked Scientists:
   
Can radio & microwaves be deflected or absorbed by using electronic devices?

Dennis O'Donnell

What do you think?

[Pumblechook]

Only passive devices, reflectors or absorbing lossy material.

[lyner]

It is quite easy to use an active device to alter the  patten of em waves. All that is needed is for the phase shift through the amplifier to be 'small' so that you can re-transmit a received wave with an appropriate amplitude and phase.
It is used for rf frequencies in stealth technology, for example, to cancel radar reflections.
I don't think it has been done for higher frequencies, tho.

[Sammy123]

yes, otherwise both your microwave, and radio would not work...which would make for a pretty moot question wouldn't it. what you should understand is that the ability of the...i shall call it "object" to deflect or absorb the radiation, is dependent on the frequency of the radiation it is being transmitted, and the inherent physical properties of that material.

for instance, your microwave, assuming you own one, which i think is a fair bet, is tuned to a frequency that makes water molecules oscillate. this could be understood as it agitates them and agitation is the quintessential theory underlying what heat is. it works so well on food because most food has water in it! to come back to your earlier question, the food absorbs the radiation emmited by your microwave via the embedded water. however, metals like aluminum reflect microwaves..causing arcing and all sorts of problems in there...dont try it if you like your oven. 'mazin...

{edit} one should specify electronic devices...all that makes an antenna is a conductor, say, copper of appropriate length. when it is electrified it transmits and when not, it absorbs.

[LeeE]

IIRC, I think some of the carbon nano tube tech can do this sort of stuff.