In a Young’s double slit experiment, two slits are illuminated with a light of wavelength 800 nm . The line joining A 1 P is perpendicular to A 1 A 2 as shown in the figure. If the first minimum is detected at P , the value of slits separation a will be : The distance of screen from slits D = 5 cm .

Step-by-step solution

The position of first minima is y = λ D 2 × a ( y is height of the point from the axis passing through the mid-point of A 1   and   A 2 ) Since the first minima is in front of the slit as shown in the figure, λ D 2 × a = a 2 ⇒ a = λ D = 800 × 10 - 9 × 5 × 10 - 2 = 2 × 10 - 4   m = 0 . 2   mm