Question

A communications satellite in orbit sends a parallel beam of signals down to earth. If these signals obey the same laws of reflection as light and are to be focussed onto a small receiving aerial, what should be the best shape of the metal 'dish' used to collect them? 

Answer 1

A communications satellite sends a parallel beam of signals down to the Earth. If these signals are to be focussed onto a small receiving aerial, then the best shape of the metal dish that can be used to collect them would be concave. The metal dish will behave like a concave mirror, which is a converging mirror.