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JEE Main 2025 (22 Jan, Shift 2) · Photoelectric Effect: Einstein's Equation

Photoelectric Effect: Einstein's Equation question from JEE Main 2025 (22 Jan, Shift 2)

Q41JEE Main 2025 · 22 JAN · SHIFT 2Medium

Photoelectric Effect: Einstein's Equation

A light source of wavelength λ\lambda illuminates a metal surface and electrons are ejected with maximum kinetic energy of 2 eV. If the same surface is illuminated by a light source of wavelength λ2\frac{\lambda}{2}, then the maximum kinetic energy of ejected electrons will be (The work function of metal is 1 eV)

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Answer: (a)

  1. hcλ=ϕ+K=1+2=3 eV\frac{hc}{\lambda} = \phi + K = 1 + 2 = 3\text{ eV}
  2. At λ2\frac{\lambda}{2}: photon energy =6 eV= 6\text{ eV}
  3. K′=6−1=5 eVK' = 6 - 1 = 5\text{ eV}
  4. So the answer is (a) 5 eV.
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