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MHT CET 2019 (2 May, Shift 1) · Bohr Model: Orbits, Speed & Angular Momentum

Bohr Model: Orbits, Speed & Angular Momentum question from MHT CET 2019 (2 May, Shift 1)

Q104MHT CET 2019 · 2 MAY · SHIFT 1Difficult

Bohr Model: Orbits, Speed & Angular Momentum

Bohr model is applied to a particle of mass ' mm ' and charge ' qq ' is moving in a plane under the influence of a transverse magnetic field ' BB '. The energy of the charged particle in the nnth level will be ( h=h = Planck's constant)

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Answer: (c)

  1. qvB=mv2r⇒r=mvqBqvB = \frac{mv^2}{r} \Rightarrow r = \frac{mv}{qB}.
  2. Bohr condition: mvr=m2v2qB=nh2π⇒v2=nhqB2πm2mvr = \frac{m^2 v^2}{qB} = \frac{nh}{2\pi} \Rightarrow v^2 = \frac{nhqB}{2\pi m^2}.
  3. Energy is only kinetic: E=12mv2=nhqB4πmE = \frac{1}{2}mv^2 = \frac{nhqB}{4\pi m}
  4. So the answer is (c) nhqB/4πmnhqB/4\pi m.
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