The photographic action of X rays

An account of theoretical considerations of the photographic action of x rays, based on the absorption process of x rays in photographic emulsions, and found to be in good agreement with experimental results, is presented in this paper. An equation giving the variation of the photographic action with wave-length is deduced. Consideration is given to the number of grains made developable per absorbed photon. The conclusion is reached that the energy required to make one grain developable is, for a given emulsion, constant for effective wave-length from 47 x.u. to 395 x.u.