Question 68: Dual Nature of Matter and Radiation

Question

The radiation pressure exerted by a 450 W light source on a perfectly reflecting surface placed at 2 m away from it, is

Accepted Answer

First, the intensity $$I$$ at a distance $$r$$ from a point light source spreading its energy isotropically is given by
$$I = \frac{P}{4\pi r^2},$$
where
$$P = 450 \, 	ext{W}$$
$$r = 2 \, 	ext{m}.$$
So,
$$I = \frac{450}{4\pi (2)^2} = \frac{450}{16\pi} \approx \frac{450}{50.27} \approx 8.96 \, 	ext{W/m}^2.$$
For a perfectly reflecting surface, the radiation pressure $$p$$ is given by
$$p = \frac{2I}{c},$$
where $$c \approx 3 	imes 10^8 \, 	ext{m/s}$$ is the speed of light.
Substituting the value of $$I$$:
$$p = \frac{2 	imes 8.96}{3 	imes 10^8} \approx \frac{17.92}{3 	imes 10^8} \, 	ext{Pa}.$$
Calculating the final value:
$$p \approx 5.97 	imes 10^{-8} \, 	ext{Pa},$$
which is approximately $$6 	imes 10^{-8} \, 	ext{Pa}.$$
Thus, the correct answer is:
Option D: $$6 	imes 10^{-8}$$ Pascals.

Answer

$3 	imes 10^{-8}$ Pascals

Answer

0

Answer

$1.5 	imes 10^{-8}$ Pascals

Answer

$6 	imes 10^{-8}$ Pascals

Dual Nature of Matter and Radiation

The radiation pressure exerted by a 450 W light source on a perfectly reflecting surface placed at 2 m away from it, is

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