Q.

In a Young's double slit experiment, if there is no initial phase difference between the light from the two slits, a point on the screen corresponding to the fifth minimum has path difference.                [2019]
 

1 5λ2  
2 10λ2  
3 9λ2  
4 11λ2  

Ans.

(3)

Given, there is no initial phase difference.

   Initial phase = δ = 0

Again, Phase difference =2πλ×Path difference

δ'=2πλ×ΔxΔx=λ2π×δ'

Now, for the fifth minima we will consider n=4 as initial phase difference is zero.

    For fifth minimum, δ'=(8+1)π=9π

    Path difference, Δx=λ2π×9π=9λ2