The ratio of longest wavelength line in the Balmer andaschen series of hydrogen spectrum is

Options

A. `5/36`
B. `7/20`
C. `7/144`
D. `5/27`

Answer

b

Explanation

Balmer series of hydrogen spectrum is given by,
`lambda_1=lambda_("Balmer") alpha[1/2^2-1/3^2]=5/36`
Paschen series of hydrogen spectrum is given by,
`lambda_2=lambda_("Balmer")alpha [1/3^2-1/4^2]=7/144`
`lambda_2/lambda_1=(7/144)/((5)/36)=7/144xx36/5=7/20`