Monochromatic radiation

In physics, monochromatic radiation is electromagnetic radiation with a single constant frequency or wavelength. When that frequency is part of the visible spectrum (or near it) the term monochromatic light is often used. Monochromatic light is perceived by the human eye as a spectral color.

When monochromatic radiation propagates through vacuum or a homogeneous transparent medium, it remains with a single constant frequency or wavelength; otherwise, it suffers refraction.