There are some aspects of light that can be easily demonstrated by using the concept of wave. However I really want to know what it would be like in term of photon point of view. So I have some question.
I know that real light is a combination plane wave in different wavelength, a Gaussian wave which can be expanded to a Fourier series. Each plane wave in the Fourier series has a quanta, which is a photon with corresponding frequency and energy. Then what is the relationship of the Gaussian wave with those infinite quantas?
In a medium, there is phase velocity and group velocity. What are they in the photon point of view? (I think a photon may be absorbed by an atom then be released after some times so the time is delayed, therefore the velocity is decreased. I think the velocity in this sense is the phase velocity. If that is true, what is the group velocity then?)
It would be great if you can link me some papers to read about. I can understand quantum physics as long as it's not too mathematically complicated.