* For a pure colour, the colour is simply the energy of the photons. Atoms have discrete stable electron orbits, and electrons moving between these levels will absorb or emit discrete levels of energy in the form of photons, which is why we have spectral lines. Reality is more complicated because part of the energy may be converted to vibrations of the atom itself (phonons).
* Another factor is the perception of colour. In physics to characterize light one measures its spectra, the intensity of the light versus its wavelength (wavelength = speed of light in vacuum / frequency). The perception of colour of these distributions isn't always always what one would expect.
* The reflection angle laws are due to the laws of conservation, see https://en.wikipedia.org/wiki/Snell%27s_law
* For a pure colour, the colour is simply the energy of the photons. Atoms have discrete stable electron orbits, and electrons moving between these levels will absorb or emit discrete levels of energy in the form of photons, which is why we have spectral lines. Reality is more complicated because part of the energy may be converted to vibrations of the atom itself (phonons).
* Another factor is the perception of colour. In physics to characterize light one measures its spectra, the intensity of the light versus its wavelength (wavelength = speed of light in vacuum / frequency). The perception of colour of these distributions isn't always always what one would expect.