What would be maximum wavelength for Brackett series of hydrogen spectrum ?

Options

A. 74583 Å
B. 22790 Å
C. 40519 Å
D. 18753 Å

Answer

C

Explanation

For Brackett series `n_(1)=4, n_(2)=5,6,7,...`
`(1)/(lambda)=R[(1)/(n_(1)^(2))-(1)/(n_(2)^(2))]`
where `R=1.0967xx10^(7)m^(-1)` called Rydberg.s constant and for maximum wavelength `n_(2)=5`
`(1)/(lambda_(max))=1.09687xx10^(7)[(1)/(4^(2))-(1)/(5^(2))]`
`=1.09687xx(9)/(400)`
`lambda_(max)=(400)/(9.87183)xx10^(-7)=40.519xxx10^(-7)`
`=40519Å`