1. The problem statement, all variables and given/known data I don't understand what E = nhv means. What does it apply to and what does the n (energy level) mean in the equation. It says in the textbook, "According to Planck, the atoms of the solid osscillate with a definite frequency depending on the solid. But in order to reproduce the results of the experiements on glowing solids, he found it necessary to accept that an atom could only have certain energies of vibration, E, those allowed by the formula E=nhv This was when they were discussing his experiment on testing the intensity of the light emitted by hot objects Later, they talk about the photoelectric effect and how E=hv is incorporated into that. They said how if a vibrating atom changed energies, the change in energy would be released as light energy and they described photons as particles with energy E proportional to the observed frwquency of the light. The definitions are confusing me. I don't get the difference between the 2 equations or what they mean, and what each of them apply to?