Emitted light has a frequency. But what 'clicks' are happening every second that give the continuous beam of light a frequency? Is it the average period between photon emissions?

Question

anonymous · Answer

The frequency of light is a measure of the rate of oscillation in the electric and magnetic fields that make up an electromagnetic wave. If you want to think of light in terms of photons its easier to think of the energy or momentum of each photon. 

If you want some physical thing to relate this to, then the frequency of an emitted radio wave is determined by the rate at which the potential difference changes across the antenna.

anonymous · Answer

This article can be very interesting for your question as it explains the photon (particle) and wave duality: http://en.wikipedia.org/wiki/De_Broglie_hypothesis

anonymous · Answer

Thanks: I was familiar with the theory, but just wanted something physical to relate to.

anonymous · Answer

Something physical can be the diffraction of light, which proves that light has wave-like properties