Upper limit of the energy of the photon and the phase change of photon   to material particles at the Scwartzschild radius
  The concept of Scwartzschild radius is extended to the photon and the upper limit imposed on the energy of a photon as a result of the three characteristics of the photon--the constancy of the velocity of light, the spin value of $1\hslash$ and the zero rest mass of the photon--is shown. Further the phase change that occurs to the photon at the Scwartzschild radius, from energy to matter as a result of vacuum fluctuations is indicated. 
C. Radhakrishnan Nair