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Photoelectric Effect: Einstein's Equation question from NEET 2026

Q2NEET 2026Easy

Photoelectric Effect: Einstein's Equation

For a metal of work function 6.6 eV, which of the following wavelengths of incident radiation does not give rise to the photoelectric effect?

(Take Planck's constant as 6.6×10−34 J s6.6 \times 10^{-34}\text{ J s})

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Answer: (c)

  1. Threshold wavelength λ0=hcϕ=1240 eV nm6.6 eV≈188 nm\lambda_0 = \dfrac{hc}{\phi} = \dfrac{1240\text{ eV nm}}{6.6\text{ eV}} \approx 188\text{ nm}
  2. Only λ>188 nm\lambda > 188\text{ nm} fails to cause emission.
  3. Of the options only 200 nm200\text{ nm} exceeds 188 nm188\text{ nm}.
  4. So the answer is (c) 200 nm.
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