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MHT CET 2025 (20 Apr, Shift 2) · Photoelectric Effect: Einstein's Equation

Photoelectric Effect: Einstein's Equation question from MHT CET 2025 (20 Apr, Shift 2)

Q45MHT CET 2025 · 20 APR · SHIFT 2Medium

Photoelectric Effect: Einstein's Equation

On a photosensitive material, when frequency of incident radiation is increased by 20%20\%, maximum kinetic energy of emitted photoelectrons increases from 0.4 eV to 0.7 eV. The work function of the material is

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Answer: (b)

  1. hν=K+ϕh\nu = K + \phi: hν=0.4+ϕh\nu = 0.4 + \phi and 1.2hν=0.7+ϕ1.2h\nu = 0.7 + \phi.
  2. 1.2(0.4+ϕ)=0.7+ϕ⇒0.48+1.2ϕ=0.7+ϕ1.2(0.4 + \phi) = 0.7 + \phi \Rightarrow 0.48 + 1.2\phi = 0.7 + \phi
  3. 0.2ϕ=0.22⇒ϕ=1.10.2\phi = 0.22 \Rightarrow \phi = 1.1 eV
  4. So the answer is (b) 1.1 eV.
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