Question

In Young's double slit experiment, the path difference between two interfering waves at a point on screen is $13.5$ times the wavelength. The point is:

• A. bright but not central bright
• B. neither bright nor dark
• C. central bright
• D. dark

Answer 1

The correct option is D dark

Given,
path difference $\left(△\right)=13.5\lambda .....\left(i\right)$
We know that,
path difference $\left(△\right)=(n+\frac{1}{2})\lambda .....\left(ii\right)$
We can write Eq. (i) in the following form
$△=(13+\frac{1}{2})\lambda .....\left(iii\right)$
From Eqs. (ii) and (iii), it is clear that there will be minima. So, the point will be dark.