When does each OCCUR?
-Please,Simplify your answers as far as possible but be scientific-
reflection occurs when photons approach a shiny surface and are reflected, according to the classical theory angle of incidence = angle of reflection, however this is untrue when reflection is explained in terms of quantum electrodynamics (QED).
Refraction is a bit complicated (to me anyway). This happens when light travels from one medium to another, this causes a change in wavelength and the speed changes.Light has to be continous, frequency has to stay constant once the photon is emitted. A very precise definition is that: the wavefunction of the photon interacts with the wavefunction of the electron and causes an oscillation in the centre of gravity of charge density.
Total Internal Reflection occurs when light is refracted and the critical angle is 90o.
Diffraction is a property of waves. This is shown by the double slit experiment. Light is confined to travel through a very small hole so according to Heisenberg's uncertainty principle the position is not spread out, so the photon must have a wide range of momentum and would travel through the two slits at the same time.
About total internal reflection... I believe that the better definition is that where incident light hits the edge of a medium at an angle >= to the critical angle which is determined by the two mediums that the light is trying to move between.
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