Wavelength is the distance of one full cycle of the oscillation made by a photon. The distance is determined by the amount of energy which a photon carries. Photons containing more energy have shorter wavelengths, and longer wavelength photons carry low energy. The electromagnetic spectrum spans a broad range of wavelengths from gamma rays which have a wavelength of 10 nm to radio waves which have a wavelength of 1012 nm. A very small part of this spectrum—extending from about 380 nm to 770 nm—can be seen by the human eye. This part of the electromagnetic spectrum is called visible light.
