A sample of hydrogen gas is excited by means of a monochromatic radiation. In the subsequent emission spectrum, `10` differenet wavelengths are obtained, all of which have enrgies greater than or equal to the energy of the abosrbed radiation. Find the intitial quantum number of the state (before abosrbing radiation).

Answer

4

Explanation

`10` emission lines `rArr ` final state `n = 5`
If the initial state were not `n = 4` in the emission spectrum, some lines with energies less than that of absorbed radiation would have been observed.
`:.` Initial state `n=4`