Question

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

• A. Bright but not central bright
• B. Neither bright not dark
• C. Central bright
• D. Dark

Answer 1

Answer: (D)

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