BITSAT 2023 Shift 1 Paper

If we assume electron in hydrogen atom takes energy 12.09‌eV from the incoming radiation, the maximum excited state of electron will be n=3. So, number of spectral lines is ‌

3(3−1)

2

=3.
Here we assume some part of energy 12.5‌eV −12.09‌eV=0.41‌eV get lost due to collision.