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.

Options

• 200

• 500

• 700

• 600

Answer 1

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 600 nm.

Explanation:

Fringe width, `beta = (lambdaD)/d`

⇒ `3 xx 10^-5 = (lambda xx 5 xx 10^-2)/(1 xx 10^-3)`

⇒ `lambda = (3 xx 10^-5 xx 10^-3)/(5 xx 10^-2)`

`lambda = 0.6 xx 10^-6` m

⇒ λ = 600 × 10^-9 nm

As a result, the required answer is 600.