Quote:
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Originally Posted by Boomerang
This takes me back to my days doing college physics, many more years ago than I care to remember!
The physical principles are quite clear - the electromagnetic waves of a radar beam are reflected by electrical conductors, such as metals, which thus give a good radar signature. Electrical insulating materials, such as wood are transparent to the electromagnetic waves, which pass through them with very little reflection or absorption. Net result = wood is transparent to a radar beam.
Above was established by Hertz in his original study of electromagnetic waves.
Cheers
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Whilst metal is a much more efficient reflector of radio frequency (rf) energy than wood what is as important are the dimensions of the reflector. The most efficient size for a reflector is half a wavelength of the frequency of the emitter.
Wavelength (λ) = Velocity of light (v)/Frequency (f)
as the velocity of light is constant (3x10^8 m/s) if you know the frequency of operation you can calculate the wavelength.
That is why the length of the aluminum strips in window (modern day chaff) is so important when jamming enemy radars and as Graham says why metal propellors of a certain size make such good reflectors.
Regards
Andy Fletcher