Monochromatic is the term used for light consisting of waves of one wavelength only. This is termed a pure spectral colour, which is comparable with a sinusoidal tone in acoustics. Light from the sun or from artificial light sources (except for lasers) is polychromatic: it contains waves of different wavelengths. Polychromaticity
Fig. 27: Monochromatic (a) and polychromatic (b) light