Radition coming from transition n = 2 to n =1 of hydrogen atoms falls on helium ions in n =1 and n =2 states. What are the possible transit ions of helium ions as they absorb energy from the radition ?
From trasitions n = 2 to n = 1
E = 13.6 (11−14)
= 13.6×34=10.2eV
Let the transitions possible on He
n = 1 to 2
E1=4×13.6(1−14)
= 40.8 e V
E1>E, Hence it is not possible
n = 1 to n = 3
E2=4×13.6(1−19)
= 48.3 e V
E2>E. Hence impossible
Similary, n = 1 to n = 4
is also not possible
n = 2 to n =3
E3=13.6×4(14−19)
= 20×13.636=7.56eV
As E3<E and E4=E
Hence E3 and E4 can be possible