In terms of Rydberg's constant `R`, the wave number of the first Balman line is

Options

A. `R`
B. `3R`
C. `(5R)/(36)`
D. `(8R)/(9)`

Answer

C

Explanation

Wave number `= (1)/(lambda) = R ((1)/(n_(1)^(2)) - (1)/(n_(2)^(2))) `
For first Balmer line `n_(1) = 2, n_(2) = 3`
`:.` Wave number `= R ((1)/(2^(2)) - (1)/(3^(2))) = R ((9 - 4)/(9 xx 4)) = (5R)/(36)`