Electromagnetic Waves Question 3
Question 3 - 2024 (27 Jan Shift 2)
An object is placed in a medium of refractive index 3 . An electromagnetic wave of intensity $6 \times 10^{8} \mathrm{~W} / \mathrm{m}^{2}$ falls normally on the object and it is absorbed completely. The radiation pressure on the object would be (speed of light in free space $=3 \times 10^{8} \mathrm{~m} / \mathrm{s}$ ):
(1) $36 \mathrm{Nm}^{-2}$
(2) $18 \mathrm{Nm}^{-2}$
(3) $6 \mathrm{Nm}^{-2}$
(4) $2 \mathrm{Nm}^{-2}$
Show Answer
Answer: (3)
Solution:
Radiation pressure $=\frac{I}{\mathrm{v}}$
$=\frac{\mathrm{I} \cdot \mu}{\mathrm{c}}$
$=\frac{6 \times 10^{8} \times 3}{3 \times 10^{8}}$
$=6 \mathrm{~N} / \mathrm{m}^{2}$
