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Question: An electron jumps from n = 4 to n = 1 state in H-atom. The recoil momentum of H-atom (in eV/C) is...

An electron jumps from n = 4 to n = 1 state in H-atom. The recoil momentum of H-atom (in eV/C) is

A

12.75

B

6.75

C

14.45

D

0.85

Answer

12.75

Explanation

Solution

The H-atom before the transition was at rest. Therefore from conservation of momentum

Photon momentum = Recoil momentum of H-atom or Precoil=hνc=E4−E1c=−0.85eV−(−13.6eV)c=12.75eVcP_{recoil} = \frac{h\nu}{c} = \frac{E_{4} - E_{1}}{c} = \frac{- 0.85eV - ( - 13.6eV)}{c} = 12.75\frac{eV}{c}