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Photoelectric Effect: Einstein's Equation question from NEET 2018

Q137NEET 2018Medium

Photoelectric Effect: Einstein's Equation

When the light of frequency 2v0v_0 (where v0v_0 is threshold frequency), is incident on a metal plate, the maximum velocity of electrons emitted is v1. When the frequency of the incident radiation is increased to 5v0v_0, the maximum velocity of electrons emitted from the same plate is v2. The ratio of v1 to v2 is

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Answer: (a)

  1. 12mv2=hν−hν0\frac{1}{2}mv^2 = h\nu - h\nu_0
  2. At 2ν02\nu_0: K1=hν0K_1 = h\nu_0; at 5ν05\nu_0: K2=4hν0K_2 = 4h\nu_0
  3. v1v2=14=12\frac{v_1}{v_2} = \sqrt{\frac{1}{4}} = \frac{1}{2}
  4. So the answer is (a) 1 : 2.
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