Q. If the total electromagnetic energy falling on a surface is U, then the total momentum delivered (for complete absorption) is
A) $\frac{U}{c}$
B) $cU$
C) $\frac{U}{c^{2}}$
D) $c^{2}U$
Explanation
(a) If the surface absorbs all the incident energy then the total momentum delivered to the surface is
$p = \frac{U}{c}$ (for complete absorption)
If the surface is a perfect reflector, then the total momentum delivered to the surface is
$P = \frac{2U}{c}$ (for complete reflection)
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.