(1) z = 4; n = 2
Let E1 be the energy of the atom in its ground state. For atom in (2n)th state E2n = [E1/(2n)2].
The maximum energy photon is emitted when electron jumps from this state to the ground state, i.e.,
When electron jumps, from n2 (= 2n) to n1 (= n) state, the energy of emitted photon is 40.8 eV. Therefore
From Eqns. (1) and (2), we have
Substituting this value of n, in Eqn. (2), we get