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Question: Answered & Verified by Expert
A 12.5 eV electron beam is used to bombard gaseous hydrogen at room temperature. The number of spectral lines emitted will be:
PhysicsAtomic PhysicsJEE MainJEE Main 2023 (12 Apr Shift 1)
Options:
  • A 1
  • B 4
  • C 2
  • D 3
Solution:
2635 Upvotes Verified Answer
The correct answer is: 3

According to Bohr's postulates, if an electron absorbs a photon with energy equal to the difference between the energies of an excited state and the ground state, it will jump to a higher energy orbital.

Considering that the energy of the colliding electron is 10.2 eV or 12.09 eV, depending on how much energy is lost during the collision. n=3 is the maximum excited state. Hence, there are spectral lines in a total of

C23=3!2!1!=3

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