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MHT CET 2026 (16 Apr, Shift 2) · Matter Waves: de Broglie Wavelength

Matter Waves: de Broglie Wavelength question from MHT CET 2026 (16 Apr, Shift 2)

Q24MHT CET 2026 · 16 APR · SHIFT 2Difficult

Matter Waves: de Broglie Wavelength

A photoemissive substance is illuminated with a radiation of wavelength λi\lambda_i so that it releases electrons with de-Broglie wavelength λe\lambda_e. The longest wavelength of radiation that can emit photoelectron is λ0\lambda_0. Expression for de-Broglie wavelength is (m = mass of electron, h = Planck's constant, C = Speed of light)

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Answer: (c)

  1. Einstein: K=hc(1λi−1λ0)K = hc\left(\dfrac{1}{\lambda_i} - \dfrac{1}{\lambda_0}\right)
  2. λe=h2mK=h2mhc(1λi−1λ0)\lambda_e = \dfrac{h}{\sqrt{2mK}} = \dfrac{h}{\sqrt{2mhc\left(\frac{1}{\lambda_i}-\frac{1}{\lambda_0}\right)}}
  3. λe=[h2mc(1λi−1λ0)]1/2\lambda_e = \left[\dfrac{h}{2mc\left(\frac{1}{\lambda_i}-\frac{1}{\lambda_0}\right)}\right]^{1/2}
  4. So the answer is (c), with the whole bracket in the denominator.
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