(A) The force exerted by a beam of light on a surface is given by the rate of change of momentum.For a beam of power $P$ incident normally:Force due t

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(A) The force exerted by a beam of light on a surface is given by the rate of change of momentum.For a beam of power $P$ incident normally:Force due to absorption $(F_a)$ $= \frac{P_a}{c} = \frac{0.70 \times P}{c}$Force due to reflection $(F_r)$ $= \frac{2 \times P_r}{c} = \frac{2 \times 0.30 \times P}{c}$Total force $F = F_a + F_r = \frac{P}{c} (0.70 + 0.60) = \frac{1.30 \times P}{c}$Given $P = 10 \, W$ and $c = 3 \times 10^8 \, m/s$:$F = \frac{1.30 \times 10}{3 \times 10^8} = \frac{13}{3} \times 10^{-8} \approx 4.33 \times 10^{-8} \, N$.

Class 12 Physics Dual Nature of Radiation and matter Radiation Force and Pressure

Difficult

$A$ beam of white light is incident normally on a plane surface absorbing $70\%$ of the light and reflecting the rest. If the incident beam carries $10\,W$ of power,find the force exerted by it on the surface :-

A
$4.33 \times 10^{-8} \, N$
B
$5.76 \times 10^{-8} \, N$
C
$10.11 \times 10^{-6} \, N$
D
None

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Dual Nature of Radiation and matter

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Radiation Force and Pressure

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$A$ beam of white light is incident normally on a plane surface absorbing $70\%$ of the light and reflecting the rest. If the incident beam carries $10\,W$ of power,find the force exerted by it on the surface :-

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$A$ flashlight of intensity $9 \, W/cm^2$ illuminates a perfectly reflective surface of area $300 \, cm^2$. The average force exerted on the surface due to the incident light photons is

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