Question

A radiation of energy E falls normally on a perfectly reflecting surface. The momentum transfered to the surface is:

• A. $E/c$
• B. $E/c^2$
• C. $Ec$
• D. $2E/c$

Answer 1

Answer: (D)

Here momentum transferred is given as $P_{transferred}=P_1-P_2$
$P_1=\frac{E}{c}$
$P_2=-\frac{E}{c}$
so $P=\frac{E}{c}-(-\frac{E}{c})=\frac{2E}{c}$