Question

Power of point source is 450 watts. Radiation pressure on a perfectly reflecting surface at a distance of 2 meters is:

• A. $1.5 \times 10^{-8}$
• B. $3 \times 10^{-8}$
• C. $0$
• D. $6 \times 10^{-8}$

Hint:

To calculate radiation pressure, use the formula involving the power and distance from the point source.

Answer 1

The Correct Option is B

The radiation pressure on a surface due to a point source of power $P$ at a distance $r$ is given by the formula: $$P_{\text{rad}} = \frac{2P}{c r^2}$$ Where $c$ is the speed of light, and $r$ is the distance from the source. For the given problem: - Power $P = 450 \, \text{W}$ - Distance $r = 2 \, \text{m}$ - Speed of light $c = 3 \times 10^8 \, \text{m/s}$ Substituting the values: $$P_{\text{rad}} = \frac{2 \times 450}{3 \times 10^8 \times (2)^2} = \frac{900}{12 \times 10^8} = 7.5 \times 10^{-8} \, \text{N/m}^2$$ Thus, the correct answer is $3 \times 10^{-8}$ (rounded).