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JEE Main 2010 (AIEEE) · Photons: Energy, Momentum & Radiation Pressure

Photons: Energy, Momentum & Radiation Pressure question from JEE Main 2010 (AIEEE)

Q34JEE Main 2010 · AIEEEMedium

Photons: Energy, Momentum & Radiation Pressure

If a source of power 4 kW4\text{ kW} produces 102010^{20} photons/second, the radiation belongs to a part of the spectrum called

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Answer: (a)

  1. Energy per photon E=4×1031020=4×10−17 J≈250 eVE = \dfrac{4\times10^{3}}{10^{20}} = 4\times10^{-17}\text{ J} \approx 250\text{ eV}
  2. λ=hcE=6.6×10−34×3×1084×10−17≈5×10−9 m=5 nm\lambda = \dfrac{hc}{E} = \dfrac{6.6\times10^{-34}\times3\times10^{8}}{4\times10^{-17}} \approx 5\times10^{-9}\text{ m} = 5\text{ nm}
  3. λ≈50 A˚\lambda \approx 50\text{ Å} lies in the X-ray region.
  4. So the answer is (a) X-rays.
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