(B) 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:$1$. Force

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(B) 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:$1$. Force due to absorbed part $(70 \%)$: $F_{abs} = \frac{P_{abs}}{c} = \frac{0.7 P}{c}$$2$. Force due to reflected part $(30 \%)$: $F_{ref} = \frac{2 P_{ref}}{c} = \frac{2 \times 0.3 P}{c} = \frac{0.6 P}{c}$Total force $F = F_{abs} + F_{ref} = \frac{0.7 P + 0.6 P}{c} = \frac{1.3 P}{c}$Given $P = 10 \ W$ and $c = 3 \times 10^8 \ m/s$:$F = \frac{1.3 \times 10}{3 \times 10^8} = \frac{13}{3} \times 10^{-8} \ N \approx 4.33 \times 10^{-8} \ N$.

Class 12 Physics Dual Nature of Radiation and matter 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,the force exerted by it on the surface is

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A
$3.3 \times 10^{-8} \ N$
B
$4.33 \times 10^{-8} \ N$
C
$2.3 \times 10^{-8} \ N$
D
$3.53 \times 10^{-8} \ N$

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Dual Nature of Radiation and matter

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Radiation Force and Pressure

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Light falls on a non-reflecting surface normally. If the average force exerted on a surface with area $15 \text{ cm}^2$ during a $20 \text{ minute}$ time interval is $10^{-6} \text{ N}$,then the energy flux (intensity) of light is (Velocity of light $= 3 \times 10^8 \text{ ms}^{-1}$)

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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,the force exerted by it on the surface is

Similar Questions

$50\, W/m^2$ energy density of sunlight is normally incident on the surface of a solar panel. Some part of incident energy $(25\%)$ is reflected from the surface and the rest is absorbed. The force exerted on $1\, m^2$ surface area will be close to $(c = 3 \times 10^8\, m/s)$.

$A$ parallel beam of light is incident normally on a plane surface absorbing $50\%$ of the light and reflecting the rest. If the incident beam carries $90 \text{ W}$ of power,the force exerted by it on the surface is ($C = 3 \times 10^8 \text{ m/s}$ is the velocity of light in air).

An astronaut floating freely in space decides to use his flashlight as a rocket. He shines a $10$ $W$ light beam in a fixed direction so that he acquires momentum in the opposite direction. If his mass is $80$ kg,how long must he shine the light to reach a velocity of $1$ $m/s$?

$A$ light bulb of power $100 \ W$ is placed at the centre of a hollow sphere of radius $10 \ cm$. If $66\%$ of the energy is converted into light,then the pressure exerted by the light on the surface of the sphere will be (Assume the surface of the sphere to be perfectly absorbing).

Light falls on a non-reflecting surface normally. If the average force exerted on a surface with area $15 \text{ cm}^2$ during a $20 \text{ minute}$ time interval is $10^{-6} \text{ N}$,then the energy flux (intensity) of light is (Velocity of light $= 3 \times 10^8 \text{ ms}^{-1}$)

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