In a biprism experiment, the wavelenght of red light used is 6850Å and that of violet light used is 4050Å. The value of n for which the `(n+2)^(th)` bright band for violet light would correponded to the `n^(th)` bright band for red light for the same setting is

Options

A. 3
B. 2
C. `2.5`
D. 4

Explanation

`x_((n+2)bv)=x_(nbr)`
`(D)/(d)(n+2)lamda_(v)=(D)/(d)nlamda_(r)`
`:.(n+2)lamda_(v)=nlamda_(r)`
`4050(n+2)=6750n`
`n(6750-4050)=8100`
`:.n=(8100)/(2700)=3`