According to the quantum theory, a photon of electromagnetic radiation of frequency v has energy E = hv where h is known as planck’ constant. According to the theory of relativity, a particle of mass m has equivalent energy E = mc2, where c is speed of light. Thus a photon can be treated as a particle having effective mass m = hv/C2. If a flash of light is sent horizontal in earth’ gravitational field, then photons while traveling a horizontal distance d would fall through a distance given by -
