Why do microwaves cause more internal body heating than infrared radiation?
Microwaves, as in the portion of the EM spectrum, are “in tune” with water specifically. Instead of being absorbed at the surface like infrared rays, they are absorbed throughout the body, since the body is semitransparent to the microwaves. The lower the frequency, the more likely bodies are to be transparent to the wave type. Microwave ovens produce microwaves such that they target food, which primarily is composed of water. Microwave ovens may produce residual infrared, but it isn’t the majority of their emissions. Many surfaces are opaque to infrared waves. IR is usually the waves used in thermal radiation, because bodies at moderate temperatures emit them as per the black body radiation models. IR are not necessarily dangerous to humans, unless they cause excessive heating. Microwaves are dangerous to humans because they are in tune with water, which comprises a significant fraction of our molecules. Radio waves are completely safe for all lifeforms, since they can easily diffract
