A photon emitted during the de-excitation of electron from a state to the first excited state in a hydrogen atom, irradiates a metallic cathode of work function
, in a photo cell, with a stopping potential of
. Obtain the value of the quantum number of the state
.
From einstein photoelectric equation, We know that
Where, is the work function
is stopping potential
So,
We have,
Then, the energy difference,
Therefore,
The value of the quantum number of the state is
.