Answer to Question #92611 in Optics for ROHIT SHARMA

Question

A double slit interference pattern is produced by a parallel beam of light passing through two slits of unequal widths 20 λ and 40 λ, respectively, where λ is the wavelength of the light used. The distance between the centres of the slits is 1,000 λ. If the fringes are observed on a screen far off from the slits (D >> 1,000 λ), calculate the separation of two adjacent maxima.

Answer 1

The separation of two adjacent maxima is given by formula

$$Δ=\frac{Lλ}{d} (1)$$

where L is the distance from the centres of the slits to the screen, λ is the wavelength of the light, d is the the distance between the centres of the slits

In our case, d=1,000 λ

Using (1) we get

Δ=L

Answer

the separation of two adjacent maxima is equal to the distance from the centres of the slits to the screen