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JEE Main 2018 (15 Apr, Shift 2) · Bohr Model: Orbits, Speed & Angular Momentum

Bohr Model: Orbits, Speed & Angular Momentum question from JEE Main 2018 (15 Apr, Shift 2)

Q106JEE Main 2018 · 15 APR · SHIFT 2Medium

Bohr Model: Orbits, Speed & Angular Momentum

Muon (μ−\mu^-) is a negatively charged (|q| = |e|) particle with a mass mμ\mu = 200 me, where me is the mass of the electron and e is the electronic charge. If μ−\mu^- is bound to a proton to form a hydrogen like atom, identify the correct statements.

(A) Radius of the muonic orbit is 200 times smaller than that of the electron.

(B) The speed of the μ−\mu^- in the nth orbit is 1200\frac{1}{200} times that of the electron in the nth orbit. (C) The ionization energy of muonic atom is 200 times more than that of a hydrogen atom. (D) The momentum of the muon in the nth orbit is 200 times more than that of the electron.

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Answer: (b)

  1. (A) r=ϵ0n2h2πme2∝1mr = \frac{\epsilon_0 n^2 h^2}{\pi m e^2} \propto \frac{1}{m}: 200 times smaller. True.
  2. (B) v=e22ϵ0nhv = \frac{e^2}{2\epsilon_0 n h} does not depend on mm: same speed. False.
  3. (C) E=me48ϵ02h2∝mE = \frac{me^4}{8\epsilon_0^2 h^2} \propto m: 200 times more. True.
  4. (D) p=mvp = mv with the same vv: 200 times more. True.
  5. So the answer is (b) (A), (C), (D).
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