The main prerequisite for this study was the external similarity of such physical processes as the refraction of light in a transparent substance and the deflection of light by the gravitational field of massive cosmic bodies. Based on the external similarity, the author put forward a hypothesis about the internal similarity of these two physical processes. This made it possible to integrate Einstein's well-known relativistic formula into the process of light propagation in electron clouds (fields) of a transparent substance. As a result of the transformations carried out, a new physical dispersion formula with a wide spectrum of action was obtained from the Einstein formula. According to the new dispersion formula, 26 refractive indices of light were calculated in 5 transparent substances in 3 states of aggregation. Comparison of the obtained indicators with laboratory indicators showed the high accuracy of the new physical formula, which amounted to ±10 -7−10 -5 in the calculated sections of the wave ranges over 100 nm. The successful application of the relativistic formula to the process of light refraction in transparent substances indicates that relativistic effects are present at the atomic-molecular level.