When an excited hydrogen atom returned to its ground state, some visible quanta were observed along with other quanta. Which of the following transitions must have occurred ?

Since some visible quanta were observed along with other quanta, electrons must have made transition from some higher state to n = 2 and then from n = 2 to n = 1.∴   Transition from 2 →1 is compulsory, because electron from n = 2 will finally fall into n = 1.