The visible light spectrum refers to the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. It ranges from approximately 400 nanometers (violet light) to 700 nanometers (red light).
The distance between successive crests of a wave, especially points in a sound wave or electromagnetic wave.
The number of complete cycles per unit time for a periodic phenomenon such as waves.
A particle representing a quantum of light or other electromagnetic radiation.