The ratio of wavelength of the lest line of Balmer series and the last line Lyman series is:

Options

A. 2
B. 1
C. 4
D. 0.5

Answer

C

Explanation

Last line of a series in a hydrogen spectrum is the line of shortest wavelength and it gives the series limit.
For last line of Balmer series,
`" "1/lambda_(b)=R[1/2^(2)-1/infty^(2)]=R/4`
`therefore" "lambda_(b)=4/R" …(i)"`
and for Lyman series, `1/lambda_(l)=R[1/1^(2)-1/infty^(2)]=R`
`therefore lambda_(l)=1/R" ...(ii)"`
`therefore lambda_(b)/lambda_(l)=4/R times R/1=4`