Properties of Microwaves
Author: J.B. Hoag
In many ways, microwaves act like light rays. They can be focused with lenses made of wax or paraffin.
They can be refracted with prisms of these materials. They can be reflected from large, plane sheets of metal, as light is reflected from plane mirrors. Metal parabolas may be used to produce parallel beams. (The maximum diameter of the parabola should be greater than two or three times the wave-length if reasonably parallel beams are to be obtained.) The waves can be diffracted by slits in metal surfaces. Interferometers can be constructed for their use. In many ways, the name quasi-optical is justified. On the other hand, microwaves will pass through dry wood, whereas light waves will not. The dielectric constant of pure water for 1-meter waves is around 80; it is around 1.3 for 1-centimeter radio waves and for light waves. Apparently the electrical constituents of water molecules cannot vibrate faster than about 1 billion times each second. Likewise, the elementary magnets or " domains " of a piece of iron cease to follow an applied magnetic field if the oscillation rate is of this same order of magnitude.