Conditions have been obtained for the existence of a steady shock wave of such an intensity that radiation pressure plays a role in determining the properties of the shock. These conditions are completely analogous to the Rankine-Hugoniot equations for ordinary shocks; they are obtained by consideration of the conservation of mass, momentum, and energy. The results are applied to hydrogen and other very light gases. The application to other media requires a much more complicated discussion of the equation of state and specific heat under extremely high pressures and temperatures. In the light gases, the thickness of the shock front is extremely large because the radiation free path, which is determined by Compton scattering, is very large. The velocity of sound in a medium under very high pressures and temperatures is also discussed, and it is found that this velocity continues to increase with increasing pressure, a condition that is necessary for the shock to be stable.

• Received 12 February 1946

DOI:https://doi.org/10.1103/PhysRev.69.514