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Question

(D) The force exerted by a light beam on a fully reflective surface is given by the formula $F = \frac{2IA \cos 	heta}{c}$,where $I$ is the intensity

Vedclass · Accepted Answer

$9.4 	imes 10^{-15} 	ext{ N}$

Vedclass · Answer

(D) The force exerted by a light beam on a fully reflective surface is given by the formula $F = \frac{2IA \cos 	heta}{c}$,where $I$ is the intensity,$A$ is the cross-sectional area,$	heta$ is the angle of incidence,and $c$ is the speed of light $(3 	imes 10^8 	ext{ m/s})$.Given values are $I = 10^{-3} 	ext{ W m}^{-2}$,$A = 20 	ext{ cm}^2 = 20 	imes 10^{-4} 	ext{ m}^2$,and $	heta = 45^{\circ}$.Substituting these values into the formula:$F = \frac{2 	imes 10^{-3} 	imes 20 	imes 10^{-4} 	imes \cos 45^{\circ}}{3 	imes 10^8}$$F = \frac{2 	imes 10^{-3} 	imes 20 	imes 10^{-4} 	imes 0.707}{3 	imes 10^8}$$F = \frac{2.828 	imes 10^{-6}}{3 	imes 10^8} \approx 9.42 	imes 10^{-15} 	ext{ N}$.Thus,the correct option is $D$.

$A$ beam of light with intensity $10^{-3} \text{ W m}^{-2}$ and cross-sectional area $20 \text{ cm}^2$ is incident on a fully reflective surface at an angle of $45^{\circ}$. The force exerted by the beam on the surface is:

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