An electromagnetic wave of intensity I falls on a surface kept in vacuum and exerts radiation pressure p on it. Which of the following are true?
a. Radiation pressure is I/c if the wave is totally absorbed
b. Radiation pressure is I/c if the wave is totally reflected
c. Radiation pressure is 2I/c if the wave is totally reflected
d. Radiation pressure is in the range I/c<p<2I/c for real surfaces