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JEE Main 2023 (6 Apr, Shift 1) · Matter Waves: de Broglie Wavelength

Matter Waves: de Broglie Wavelength question from JEE Main 2023 (6 Apr, Shift 1)

Q77JEE Main 2023 · 6 APR · SHIFT 1Medium

Matter Waves: de Broglie Wavelength

The kinetic energy of an electron, α\alpha-particle and a proton are given as 4 K,2 K4\text{ K}, 2\text{ K} and K\text{K} respectively. The de-Broglie wavelength associated with electron (λe),α(\lambda \mathrm{e}), \alpha-particle (λα)(\lambda\alpha) and the proton (λp)(\lambda p) are as follows:

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Answer: (a)

  1. λ=h2mK⇒λ∝1mK\lambda = \dfrac{h}{\sqrt{2mK}} \Rightarrow \lambda \propto \dfrac{1}{\sqrt{mK}}.
  2. Electron: me(4K)m_e(4K), tiny since me≪mpm_e \ll m_p. Proton: mpKm_pK. Alpha: (4mp)(2K)=8mpK(4m_p)(2K) = 8m_pK.
  3. Largest mKmK gives smallest λ\lambda: λα<λp<λe\lambda_\alpha < \lambda_p < \lambda_e.
  4. So the answer is (a).
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