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 ?

Options

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 lt P lt 2I//c` for real surfaces.

Answer

B

Explanation

Radiation prressure (P) lies between I/c and 2I/c for real surfaces.
When wave is fully absorbed,
radiation pressure `(P) = (Delta I )/(c ) = (I -0)/(c ) = (I)/(c )`
(when wave is fully absorved by surface, momentum of reflected wave per unit time per area =0).
When wave is fully reflected, momentum per unit time per unit area `=- I//c,`
Radiation pressure `(p) = (I)/(c ) = ((-I)/(c )) = (2I)/(c )`