Question

When measuring signal from a radio source, we receive signals from many electrons emitting arbitrary sine waves. Why do we receive the signal from lots of electrons and why do they emit signals of different frequencies, phases and amplitudes?

Answer 1

There are two process through them electrons emits electromagnetic waves.one is thermal process.by absorbing the thermal energy electrons transists at higher energy levels.higher the energy the lower its lifetime of that energy state.at any instant when we make the measurement of energy many of electrons transisting from different lower states to different higher states and many of them coming back to lower states after transmission of em waves they also sometimes absorb the energy with their nearby electrons.which affect the spectrum.

The second process in non thermal.as we are reffering the large objects of universe as radio source,they also have a measureable magnetic field.so as electron as moving charge particles with fast velocity gets accelerated at different direction according to the angle between magnetic field and velocity of electrons.so electrons feel a push towards different energy levels.so there is phase difference between electomagnetic radio waves emitted by them.as we know em waves emmitted by different energy levels have different frequencies and amplitude.these two are the reasons of arbitrary sine waves,phase difference and different frequencies and amplitude.