Why does hair appear black?

The perception of colour results from the interaction between light and an object. The colour that an object appears to be depends on the wavelengths of light that it absorbs and reflects.

Hair colour is determined by the presence of melanin, which is a pigment produced by cells in the hair follicle. Melanin comes in two forms: eumelanin and pheomelanin. Eumelanin is responsible for brown and black hair colours, while pheomelanin is responsible for red hair colours.

The amount and ratio of eumelanin and pheomelanin in a hair follicle determines the resulting hair colour. Black hair is the result of a high concentration of eumelanin and a low concentration of pheomelanin. The eumelanin absorbs all wavelengths of light, resulting in the perception of black hair.