Talbot's Law

TALBOT'S LAW (Talbot). If periodically varying in brightness light and light of constant brightness causes in the eye an impression of equal intensity, then the amount of energy delivered to the retina in these two cases is equal. In this case, the period of light change must be sufficiently small. This law was discovered by Talbot, then investigated by Helmholtz, and thoroughly studied for color vision by Lummer and Brodhun, who showed the full applicability of Talbot's Law for central vision. For peripheral vision, T. z. was theoretically derived from the ionic theory of excitation by Lazarev, who confirmed the theoretical conclusion experimentally. Lazarev showed that for all photochemical reactions, including the reaction in the retina, the same photochemical effect is obtained with the same amount of energy supplied per unit of time. T. z. is also applicable in the processes of carbon assimilation in plants under light. This is related to the photochemical nature of assimilation. T. z. is widely used for weakening light in photometry, where on the path of the beam whose brightness is desired to be weakened, a disk with a cut is placed, the width of which can be changed in a measurable way.