These waves are invisible to the human eye. Light is the part of the spectrum that stimulates the eye's retina, resulting in sight. Usually they jump right back, releasing the extra energy in the form of light. The energy levels or states can be imagined as rings or orbits around a nucleus. Electrons in outer rings are at higher energy levels than those in inner rings.
Lasers are possible because of the way light interacts with electrons.
Then it falls to the lower energy level and emits a pulse of light. The disturbing pulse and the dislodged pulse are in phase. They stimulate other excited atoms to give off energy, until a huge light pulse builds up. Learn more about the energy level of electrons in the Chemistry Gateways activity, Emission Spectra and the Bohr Atom . The electrons of different elements all move at their own frequency.