Question

In an experiment the two slits are `0.5mm`apart and the fringes are observed to`100cm`from the plane of theslits ,The distance of the`11th`bright fringe from the ist bright fringe is `9.72mm`.calcualte the wavelength
A. `4.85xx10^(-5)cm`
B. `4.85xx10^(-5)m`
C. `4.86xx10^(-7)cm`
D. `4.86xx10^(-5)cm`

Answer 1

Answer:
Given `d=.5mm =5xx10^(-2)cm,`
`X_(n)=X_(11)-X_(1)=9.72mm`
`:.X_(n)=(nlambdaD)/(d) n=11-1=10`
`rArr lambda=(X_(n)D)/(d) =(.972xx5xx10^(-2))/(10xx100) rArr lambda=4.86xx10^(-5)cm`