Em Waves Question 105
Question: A plane electromagnetic wave is incident on a plane surface of area A, normally and is perfectly reflected. If energy E strikes the surface in time t then force exerted on the surface is (c =speed of light)
Options:
A) $ \frac{2E}{Atc} $
B) $ \frac{E}{2c} $
C) $ \frac{2E}{ct} $
D) zero
Show Answer
Answer:
Correct Answer: C
Solution:
[c] Incident momentum, $ p=\frac{E}{c} $ For perfectly reflecting surface with normal incidence $ \Delta p=2p=\frac{2E}{c} $ ; $ F=\frac{\Delta p}{\Delta t}=\frac{2E}{ct} $ ;
BETA
