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NEET 2014 (AIPMT) · Momentum & Radiation Pressure

Momentum & Radiation Pressure question from NEET 2014 (AIPMT)

Q13NEET 2014 · AIPMTMedium

Momentum & Radiation Pressure

Light with an energy flux of 25 ×\times 104 W m−2{}^{-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

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Answer: (b)

  1. Perfect reflector: F=2IAcF = \dfrac{2IA}{c}
  2. F=2×25×104×15×10−43×108=7503×108F = \dfrac{2 \times 25 \times 10^4 \times 15 \times 10^{-4}}{3 \times 10^8} = \dfrac{750}{3 \times 10^8}
  3. F=2.50×10−6 NF = 2.50 \times 10^{-6}\ \text{N}, so the answer is (b).
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