Electronic transition in `He^(+)` ion takes from `n_(2) " to " n_(1)` shell such that :
`2n_(2)+3n_(1)=18`
`2n_(2)+3n_(1)=6`
What will be the total number of photons emitted when electrons transit to `n_(1)` shell?

Options

A. 21
B. 15
C. 20
D. 10

Answer

D