Question

In a double slit experiment with monochromatic light, fringes are obtained on a screen placed at some distance from the plane of slits. If the screen is moved by 5 × 10-2 m towards the slits, the change in fringe width is 3 × 10-3 cm. If the distance between the slits is 1 mm, then the wavelength of the light will be _______ nm.

Answer 1

The correct answer is 600
Fringe width is as follows ,
$β = \frac{λD}{d}$
$⇒ |dβ| = \frac{λ}{d} |d(D)|$
$⇒ 3 × 10^{-3} cm$
$= \frac{λ}{1 mm} ( 5 × 10^{-2} m )$
$⇒ λ = \frac{3 × 10^{-8}}{5 × 10^{-2}}$ m
⇒ λ = 600 nm
∴ The wavelength of the light will be 600 nm.