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)
BITSAT
Physics
Dual Nature of Matter
2021
BITSAT 2021
BITSAT Physics Question (2021) — Solution
Options
- A. 2 E Atc
- B. E 2 c
- C. 2 E ct
- D. zero
Answer
C. 2 E ct
Step-by-step solution
Incident momentum, p= E c For perfectly reflecting surface with normal incidence p=2 p= 2 E c ; F = p t = 2 E c t
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