If `lamda_1 " and " lamda_2` are the wavelengths of the first members of the Lyman and paschen series respectively, then `lamda_1/lamda_2` is equal to

Options

A. `1:3`
B. `30:1`
C. `7:50`
D. `7:108`

Answer

D

Explanation

For lyman series , `1/lamda_1 = R(1/1^2 - 1/2^2)`
`therefore 1/lamda_1 = (3R)/(4) therefore lamda_1 = (4)/(3R)`
For paschen series , `1/lamda_2 = r[1/3^2 - 1/4^2]`
`therefore 1/lamda_2 = R [7/144] therefore lamda_2 = (144)/(7R)`
`therefore lamda_1/lamda_2 = (4)/(3R)xx(7R)/(144) = 7/108`