1. The problem statement, all variables and given/known data A spherical shell of diameter D, filled with hydrogen orbits the earth. The average intensity of solar radiation, in a plane perpendicular to the rays is [itex]1.4kW/m^2[/itex]. Calculate the total force of solar radiation pushing it off its orbit as a function of the shell's albedo. 2. Relevant equations [tex]F = P.A [/tex] [tex]A = (4\pi r^2)/2 = (\pi d)/2[/tex] [tex]P_r = \left\langle S\right\rangle/c = I/c[/tex] 3. The attempt at a solution So far I have used all the substitutions which is simple. What I'm not sure is how to incorporate the albedo. So far I have assumed that all incident radiation is absorbed. Can I add the coefficient as [itex](1 + a)[/itex] where a = albedo to the front of momentum. Also, my calculations show that reflected incident rays are sent back the way they come from when/if they are reflected. A plane wave incident on a spherical object though would not reflect back in the direction it came from unless it was on the horizontal axis. My only idea would be to use a solid angle? is this along the right lines?