An active remote sensing technique similar to seismic reflection that uses pulses of microwaves instead of sound. Unlike acoustic images which show differences in density, radar images show differences in textures.
Smooth surfaces are bright , the rougher the surface the darker it appears.
Locations from which no signal returns appear black. The resolution of a radar image is a function of the band,the polarization , the sensor, and the platform from which the sensor operates. Unlike the human brain computers can record bands seperately and mix any combination you want to use later. If the space between to objects is smaller then the smallest wavelength in that band, no waves will pass between. The return signals will arrive simultaneously and the image will show a single surface.