The ratio of the wave lengths of the first line in the Lyman series of the spectrum of Hydorgen atom and the first line in the Balmer series of the spectrum of `He^(+)` is 

Options

A. `20//27`
B. `27//20`
C. `27//5`
D. `5//27`

Answer

A

Explanation

`bar(upsilon) = Z^2 R [1/(1^2) - 1/(2^2)] and lambda = 1/(bar(upsilon))`
`(lambda_H)/(lambda_(He^+)) = ((1)^2 (1/((1)^2) - 1/((2)^2)))/((2^2) (1/((2)^2) - 1/((3)^2))) = (27)/(5)`