On absorbing a photon by H-atom, an electron got excited and reached fifth orbit. When the excited atom returned to its ground state, visible and other quanta were emitted. Radiation of what wavelength must have been emitted ? Explain it.

Visible region indicates the fall of electron to the second orbit. After this, the transition 2 →1 must take place for the atom to return to its ground state (n = 1). Hence:                                    ν-=109678112−122cm−=82258cm−or                               1λ=182258cm−=1.22×10−5cm                                      =1.22×10−5cm×108Ao1cm=1220Ao