Key points are not available for this paper at this time.
It is assumed that surfaces showing low gloss consist of small elementary facets which may be set at any angle to the mean surface. These facets may be of two types, one diffusing a proportion of the incident flux according to Lambert's law, and the other reflecting, at the specular angle, a proportion s of the incident flux, where s is determined by Fresnel's equation and is dependent on the refractive index of the material. On these assumptions formulae are obtained whereby the emergent flux E can be resolved into its diffuse and specular components R and M and from which the proportional areas B of the mirror facets, set at different angles to the mean surface, can be calculated. The use of the equations is illustrated by analysing two families of curves obtained by means of an apparatus which is described and relating to light scattered from a surface of Bristol board and from a surface of magnesium-oxide smoke deposited on plane glass.
Wilfred W. Barkas (Wed,) studied this question.