Visible light

This corresponds to electromagnetic radiation in the wavelength range $3.84 \times 10^{14} \, {\rm Hz}$ to $7.69 \times 10^{14} \, {\rm Hz}$ The atmosphere is transparent in this band, which is possibly why we have developed vision in this frequency range.

Visible radiation is produced when electrons in the outer shell of atoms jump from a higher energy level to a lower lenergy level. These are used in sources of visible radiation as well as detectors. Black body radiation from objects at a temperature of a few thousand Kelvin is another source of visible light.

Colour is our perception of the relative contribution from different frequencies. Different combinations of the frequencies can produce the same colour.