How Light Works
Light is simply a form of energy (or electromagnetic radiation) made up of many small particle-like packets, with enery and momentum but no mass, that can be released by an atom. These particles are the basic components of light and are known as light photons.
Electrons orbiting the nucleus within atoms are said to be at various "energy levels". This energy level depends on many things such as speed and distance from nucleus. As well, electrons of different energy levels are said to be in different orbitals around the atom's nucleus.When electrons become excited their energy level increases and they move to a higher level orbital. Generally the higher the energy level, the higher the orbital, and the further away the electron moves from the nucleus. When energy is passed into an atom the electrons may become temporarily excited and move to a higher orbital. This excited position is held for only a small fraction of a second until it is drawn back by the nucleus and returns to its original energy level. When it does this it has to release its extra energy, which it does in the form of a photon, and in some cases a light photon.
The wavelength of the light emmited depends on the amount of energy released by the electron, and thus the type of atom as well. The wavelength of the light determines the color of light we see.