Question

When a hydrogen atom emits a photon on going from recoil speed?

Answer 1

When a hydrogen atom initially at rest emits a photon resulting in transition n=5→n=1 , its recoil speed can be calculated as follows. Therefore the recoil speed of hydrogen atom is 4.36 m/s.

Answer 2

The energy of ground state electron in Hydrogen atom is -13.6 eV. Now, it absorbs 12.1 eV energy and hence, its energy increases to -13.6 + 12.1 = -0.85 eV. For hydrogen, Z=1; Therefore, the electron jumps to 4 orbit on absorbing 12.1 eV energy.