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MHT CET 2024 (2 May, Shift 1) · Photoelectric Effect: Einstein's Equation

Photoelectric Effect: Einstein's Equation question from MHT CET 2024 (2 May, Shift 1)

Q64MHT CET 2024 · 2 MAY · SHIFT 1Medium

Photoelectric Effect: Einstein's Equation

When a metallic surface is illuminated with a radiation of wavelength ' λ\lambda ', the stopping potential is ' VV '. If the same surface is illuminated with radiation of wavelength ' 3λ3\lambda ', the stopping potential is ' (V6)\left(\frac{V}{6}\right) '. The threshold wavelength for the surface is

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Answer: (c)

  1. hcλ−ϕ=eV\frac{hc}{\lambda} - \phi = eV and hc3λ−ϕ=eV6\frac{hc}{3\lambda} - \phi = \frac{eV}{6}
  2. Multiply the second by 6 and equate: 2hcλ−6ϕ=hcλ−ϕ\frac{2hc}{\lambda} - 6\phi = \frac{hc}{\lambda} - \phi
  3. 5ϕ=hcλ5\phi = \frac{hc}{\lambda}
  4. λ0=hcϕ=5λ\lambda_0 = \frac{hc}{\phi} = 5\lambda. So the answer is (c) 5λ5\lambda.
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