I know in classical physics we calculate the energy based on the Amplitude. I also know we calculate the energy in QM based on Frequency. I know also that it was experimentally deduced that it is the freq. based on the photo electric effect...and so on... What I'm interested is in the connection ? Why ? Energy: Does the quantum(freq) averages over the myriad of atoms to become classical effect (amplitude) ? OR there is no connection ? Does the meaning of ENERGY in micro and macro world in those two cases have different meaning ?