Light with an energy flux of 18 w / m^2 or Wm^-2 falls on a non-reflecting surface at normal to

step 1 Hi friends, here it is given. Light of intensity, 18 watt per meter square, falls on a non -refl

Light with an energy flux of 18 w / m^2 or Wm^-2 falls on a...

Light with an energy flux of $18 \mathrm{w} / \mathrm{m}^{2}$ or $\mathrm{Wm}^{-2}$ falls on a non-reflecting surface at normal to surface. If the surface has an area of $20 \mathrm{~m}^{2}$. The average force exerted on the surface during 30 minutes is (A) $6.48 \times 10^{5} \mathrm{~N}$ (B) $3.60 \times 10^{2} \mathrm{~N}$ (C) $1.2 \times 10^{-6} \mathrm{~N}$ (D) $2.16 \times 10^{-3} \mathrm{~N}$

Light with an energy flux of $18 \mathrm{w} / \mathrm{m}^{2}$ or $\mathrm{Wm}^{-2}$ falls on a non-reflecting surface at normal to surface. If the surface has an area of $20 \mathrm{~m}^{2}$. The average force exerted on the surface during 30 minutes is
(A) $6.48 \times 10^{5} \mathrm{~N}$
(B) $3.60 \times 10^{2} \mathrm{~N}$
(C) $1.2 \times 10^{-6} \mathrm{~N}$
(D) $2.16 \times 10^{-3} \mathrm{~N}$

Key Concepts

Energy Flux

Energy flux, commonly termed intensity, is the amount of energy passing through a unit area per unit time. This concept is crucial in understanding how energy is delivered by electromagnetic waves such as light, and it forms the basis for calculating the energy intercepted by surfaces in various physical applications.

Radiation Pressure

Radiation pressure is the pressure exerted by electromagnetic radiation upon any surface due to the transfer of momentum from the photons. For a non-reflecting (perfectly absorbing) surface, the radiation pressure is calculated by dividing the energy flux by the speed of light, which quantifies the force per unit area experienced by the surface.

Momentum of Electromagnetic Radiation

Electromagnetic radiation carries momentum as well as energy, and the transfer of this momentum to a surface results in a measurable force. This principle underlies the determination of radiation pressure and is applicable in scenarios ranging from solar sails in space exploration to optical tweezers in laboratories.

Force Calculation from Radiation Pressure

The force exerted on a surface by electromagnetic radiation is computed by multiplying the radiation pressure by the area of the surface over which the light is incident. This method allows for the estimation of the average force even over extended time periods, as long as the intensity and area remain constant, integrating the momentum transfer over time.

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