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NTA Abhyas 2020
Exam
NTA Abhyas
Year
2020
Subject
Physics
Chapter
Electromagnetic Waves

NTA Abhyas 2020 · Physics · Electromagnetic Waves

A& 50Wm^ - 2 energy density of sunlight is incident normally on the...

A& 50Wm−250Wm^{- 2}energy density of sunlight is incident normally on the surface of a solar panel. Some part of incident energy (2525 %) is reflected from the surface and the rest is absorbed. The force exerted on 1m21m^{2} surface area will be close to (c=3×108ms−1)\left(c = 3 \times {10}^{8}ms^{- 1}\right)

Options

  1. A15×10−8N15 \times {10}^{- 8}N
  2. B20×10−8N20 \times {10}^{- 8}N
  3. C10×10−8N10 \times {10}^{- 8}N
  4. D35×10−8N35 \times {10}^{- 8}N

Correct answer

B. 20×10−8N20 \times {10}^{- 8}N

Step-by-step solution

The pressure exerted by the photons

P=0.75×Ic+0.25×2IcP = 0.75 \times \dfrac{I}{c} + 0.25 \times \dfrac{2I}{c} ( PP = pressure, cc = speed of light, II = intensity )

P=1.25×IcP = 1.25 \times \dfrac{I}{c}

We know the force can be computed using

F=P×AF = P \times A & ( FF = force, PP = pressure, AA = area )

F=1.25×(50×13×108)<br/><br/>F = 1.25 \times \left(\dfrac{50 \times 1}{3 \times 1{0}^{8}}\right)<br /><br />F = 20.83 ×10−8N\times1{0}^{- 8}N

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