What do REFLECTION, ABSORBTION and EMISSION mean in physics?
Reflection is when an incoming wave bounces off a surface and returns, the returned wave will be out of phase by 180 degrees. Also, the angle of incidence equals the angle of reflection. To understand absorption and emission you need to consider an atom. Inside an atom there is a nucleus surrounded by orbiting atoms in different shells with a higher energy moving outwards from the nucleus. An incoming wave has an energy associated with it. In absorption the energy of the wave is absorbed by the atom and bumps an electron up to a higher energy level. In emission the electron which was previously bumped up falls back down to a lower energy level. The excess energy is emitted. Electrons are always in the lowest energy level possible.
