Monochromatic radiation

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

No radiation can be totally monochromatic,[1] since that would require a wave of infinite duration as a consequence of the Fourier transform's localization property (cf.

In practice, "monochromatic" radiation — even from lasers or spectral lines — always consists of components with a range of frequencies of non-zero width.

This phenomenon is the basis of the science of spectroscopy, and is exploited in fluorescent lamps and the so-called neon signs.

[2][3] In the technique of spectroscopic analysis, a material sample is exposed to monochromatic radiation, and the amount that is absorbed is measured.