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NEET 1991 (AIPMT) · Photoelectric Effect: Einstein's Equation

Photoelectric Effect: Einstein's Equation question from NEET 1991 (AIPMT)

Q173NEET 1991 · AIPMTMedium

Photoelectric Effect: Einstein's Equation

Photoelectric work function of a metal is 1 eV. Light of wavelength λ\lambda = 3000 Å falls on it. The photo electrons come out with a maximum velocity

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Answer: (d)

  1. E=124003000≈4.13E = \frac{12400}{3000} \approx 4.13 eV, so Kmax=4.13−1=3.13K_{max} = 4.13 - 1 = 3.13 eV ≈5.0×10−19\approx 5.0 \times 10^{-19} J
  2. v=2Km=2×5.0×10−199.1×10−31≈1.05×106v = \sqrt{\frac{2K}{m}} = \sqrt{\frac{2 \times 5.0 \times 10^{-19}}{9.1 \times 10^{-31}}} \approx 1.05 \times 10^{6} m/s
  3. So the answer is (d) 10610^{6} m/s.
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