What transition in `He^(o+)` ion shall have the same wave number as the first line in Balmer series of H atom ?

Options

A. `7 rarr 5`
B. `6 rarr 4`
C. `5 rarr 3`
D. `4 rarr 2`

Answer

B

Explanation

For H atom balmer line in series is
`E_(1) - E_(2) = (1E_(1)(H))/((3)^(2)) - (E_(1)(H))/((2)^(2)) = (5E_(1)(JH))/(36)`
For `He^(o+) "ion" (Z = 2)`
`E_(6) - E_(4) = - (E_(1)(H) xx (2)^(2))/(n^(2)) - (E_(1)(H) xx (2)^(2))/(4^(2))`
`= - E_(1)(H) xx 2^(2)|(16 - 36)/(16 xx 36)|`
`= (4 xx 20)/(36 xx 16) E_(1)(H) = (5E_(1)(H))/(36)`