The first emission line of Balmer series in H spectrum has the wave number equal to :

Options

A. `(9R)/(400)cm^(-1)`
B. `(7R)/(144)cm^(-1)`
C. `(3R)/(4)cm^(-1)`
D. `(5R)/(36)cm^(-1)`

Answer

D

Explanation

For Balmer series, `n_(1)=2` and `n_(2)=3, 4, 5 .....`
`bar(v)`(for first line)`=R[(1)/(2^(2))-(1)/(3^(2))]=R((1)/(4)-(1)/(9))=(5R)/(36) cm^(-1)`.