In the given figure, the energy levels of hydrogen atom have been shown along with some transitions marked A, B, C, D and E.
The transitions A, B and C respectively represent :

Solution

Physics sir · 3 steps

Read each arrow twice: the bottom level names the series, the gap to the top level gives the member number.

1. Series from the bottom. The level an electron falls to fixes the series. Ending at n = 1 is Lyman, ending at n = 2 is Balmer, and ending at n = 3 is Paschen.
2. Member from the gap. The first member comes from the level just above, the second from two levels above, and so on. So the member number is nᵤₚₚₑᵣ - n_(lower). A jump from the continuum (n = ∞, 0 eV) gives the series limit, the shortest wavelength of that series.

   Transition	From → to	Series	Which line
   A	∞ → 1	Lyman	series limit
   B	5 → 2	Balmer	5 - 2 = 3, third member
   C	5 → 3	Paschen	5 - 3 = 2, second member
   D (for comparison)	4 → 2	Balmer	4 - 2 = 2, second member

3. So. A is the series limit of the Lyman series, B is the third member of the Balmer series and C is the second member of the Paschen series. That is option (c).

The idea to keep. Lower level gives the series, and nᵤₚₚₑᵣ - n_(lower) gives the member number. A fall from the continuum is always the series limit, never the first member.

Answer from the NTA final answer key. Solution by PrepWiser.