Light Quest
Where do photons come from?
To understand where photons come from, let's take a closer look at the atom:
 
protons neutrons and electrons
In the center of every atom is a tiny, dense nucleus. The nucleus contains two kinds of particles: neutrons, which have no charge, and positively charged protons. Negatively charged particles called electrons orbit around the nucleus in different layers, or orbitals. (Unlike this diagram, there is a vast space between the nucleus and the electron orbitals. In a gold atom, if the nucleus were one foot in diameter, then the outermost electron would be 3.3 miles away!)

These orbitals surrounding the nucleus have different levels of energy - the farther away each is from the nucleus, the more energy it has. In each orbital, electrons are moving at the speed of light. But electrons can also jump between orbitals, a process that takes energy. If electrons jump to an outer orbital, they use energy. But if they jump to an inner orbital, they give up energy. This energy is released as a tiny packet of light energy, or a photon.