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JEE Main 2026 (28 Jan, Shift 1) · Matter Waves: de Broglie Wavelength

Matter Waves: de Broglie Wavelength question from JEE Main 2026 (28 Jan, Shift 1)

Q13JEE Main 2026 · 28 JAN · SHIFT 1Medium

Matter Waves: de Broglie Wavelength

The ratio of de Broglie wavelength of a deuteron with kinetic energy EE to that of an alpha particle with kinetic energy 2E2E, is n:1n : 1. The value of nn is ______.

(Assume mass of proton == mass of neutron)

Numerical answer type. Work it out, then open the answer.

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Answer: 2

  1. λ=h2mK⇒λ∝1mK\lambda = \dfrac{h}{\sqrt{2mK}} \Rightarrow \lambda \propto \dfrac{1}{\sqrt{mK}}.
  2. Deuteron: m=2mpm = 2m_p, K=EK = E, so mK=2mpEmK = 2m_pE. Alpha: m=4mpm = 4m_p, K=2EK = 2E, so mK=8mpEmK = 8m_pE.
  3. λdλα=82=2\dfrac{\lambda_d}{\lambda_\alpha} = \sqrt{\dfrac{8}{2}} = 2
  4. So n=2n = 2.
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