What is "Wavelength of light"?

Light is a kind of electromagnetic wave and has various wavelengths such as visible light, invisible ultraviolet light and infrared light

Description

Light is a kind of the same electromagnetic wave as the electric wave. It has various wavelengths such as visible light, invisible ultraviolet light and infrared light.

Light source used for photoelectric sensors is four types that they are blue, green, red and infrared.