To explain observations that did not fit the classical wave model of light in particular?

Question

the frequency dependence of light's energy and the ability of matter and radiation to be in thermal equalibrium (the theoretical physics) what is the frequency of light's energy mean?

Answer 1

Since light is an electromagnetic wave the frequency is the time domain frequency of the oscillations in the electric and magnetic fields, which for visible light is in the range of about 5 to 7.5 x 10^14 Hz.