> nitpick: it's not inverse fourth power, it's just inverse square with twice the distance, which is 1/((2 * distance) ^ 2) = 1/(4 * distance ^ 2) No. For a d

> nitpick: it's not inverse fourth power, it's just inverse square with twice the distance, which is 1/((2 * distance) ^ 2) = 1/(4 * distance ^ 2) No. For a diffuse reflection, the amount of light hitting your target is inverse square. And then it is scattered and inverse square back on the return journey. 1/x^2 * 1/x^2 = 1/x^4. https://en.wikipedia.org/wiki/Radar#Radar_range_equation https://en.wikipedia.org/wiki/Radar#Radar_range_equation "In the common case where the transmitter and the receiver are at the same location, Rt = Rr and the term Rt² Rr² can be replaced by R^4, where R is the range." (This all assumes that your target is smaller than the beam size, of course-- which is not as true for the two cases of a radar altimeter or a doppler radar as it is for e.g. tracking aircraft... but it's still close enough in practice).