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JEE Main 2026 (28 Jan, Shift 2) · Photons: Energy, Momentum & Radiation Pressure

Photons: Energy, Momentum & Radiation Pressure question from JEE Main 2026 (28 Jan, Shift 2)

Q2JEE Main 2026 · 28 JAN · SHIFT 2Easy

Photons: Energy, Momentum & Radiation Pressure

Number of photons of equal energy emitted per second by a 6 mW laser source operating at 663 nm is ________.

(Given: h=6.63×10−34h = 6.63 \times 10^{-34} J.s and c=3×108c = 3 \times 10^{8} m/s)

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Answer: (d)

  1. E=hcλ=(6.63×10−34)(3×108)663×10−9=3×10−19 JE = \frac{hc}{\lambda} = \frac{(6.63 \times 10^{-34})(3 \times 10^{8})}{663 \times 10^{-9}} = 3 \times 10^{-19}\text{ J}
  2. n=PE=6×10−33×10−19=2×1016 s−1n = \frac{P}{E} = \frac{6 \times 10^{-3}}{3 \times 10^{-19}} = 2 \times 10^{16}\text{ s}^{-1}
  3. So the answer is (d) 2×10162 \times 10^{16}.
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