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JEE Main 201816 AprilOnline
Exam
JEE Main
Year
2018
Date
16 April
Mode
Online
Subject
Physics
Chapter
Atomic Physics

JEE Main 2018 · 16 April · Online · Physics · Atomic Physics

Both the nucleus and the atom of some element are in their...

Both the nucleus and the atom of some element are in their respective first excited states. They get de-excited by emitting photons of wavelengths λN,λA{\lambda}_{N}, {\lambda}_{A} respectively. The ratio λNλA\dfrac{{\lambda}_{N}}{{\lambda}_{A}} is closest to:

Options

  1. A10−1{10}^{- 1}
  2. B10−6{10}^{- 6}
  3. C1010
  4. D10−10{10}^{- 10}

Correct answer

B. 10−6{10}^{- 6}

Step-by-step solution

λNλa=EaEN\dfrac{{\lambda}_{N}}{{\lambda}_{a}} = \dfrac{{E}_{a}}{{E}_{N}}, where EaandEN{E}_{a}and{E}_{N} are energies of photons from atom and nucleus respectively. EN{E}_{N} is of the order of MeVMeV and Ea{E}_{a} in few eVeV. So, λNλa=10−6\dfrac{{\lambda}_{N}}{{\lambda}_{a}} = {10}^{- 6}.
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