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Electromagnetic Waves question

2014 · Q118
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Electromagnetic Waves question

2014 · Q118

NEETPhysicsElectromagnetic WavesMCQ+4 / −1
Light with an energy flux of 25 ×\times× 104 W m−-−2 falls on a perfectly reflecting surface at normal incidence. If the surface area is 15 cm2, the average force exerted on the surface is
  1. A
    1.25 ×\times× 10−-−6 N
  2. B
    2.50 ×\times× 10−-−6 N
  3. C
    1.20 ×\times× 10−-−6 N
  4. D
    3.0 ×\times× 10−-−6 N
View written solutionFree

Correct answer: B

For a perfectly reflecting surface, the average force exerted on the surface is

F = 2IAc{{2IA} \over c}c2IA​

= 2×25×104×15×10−43×108{{2 \times 25 \times {{10}^4} \times 15 \times {{10}^{ - 4}}} \over {3 \times {{10}^8}}}3×1082×25×104×15×10−4​

= 2.50 ×\times× 10−-−6 N

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