What is the shortest wavelength present in the Paschen series of spectral lines?

Options

A. 6563 Å
B. 820 nm
C. 911 nm
D. 656 nm

Answer

B

Explanation

For Paschen series m = 3
Shortest wavelength `n=oo`
`(1)/(lambda)=R((1)/(m^(2))-(1)/(n^(2)))`
`:. (1)/(lambda)R((1)/(3^(3))-(1)/(oo^(2)))`
` :. (1)/(lambda)=R((1)/(9))`
`:. (9)/(R)=(9)/(1.097xx10^(7))=820 nm`