The frequency of radiation emitted when the electron falls from n = 4 to n = 1 in a hydrogen atom will be
(Given ionization energy of H = 2.18 × 10−18 J atom−1 and h = 6.625 × 10−34Js)
Eionisation = E∞ − En = 13.6Z2effn2ev
= [13.6Z2n22 − 13.6Z2n21]
E = hv = 13.6 × 12(1)2 − 13.6 × 12(4)2,
hv = 13.6 − 0.85
∴ h = 6.625 × 10−34
v = 13.6 − 0.856.625 × 10−34 × 1.6 × 10−19 = 3.08 × 1015 s−1