2015 AIPMT-I Wave OpticsYoung's double slit and diffraction Medium Question 30 of 40 in Wave Optics

In a double slit experiment, the two slits are 1 mm apart and the screen is placed 1 m away. A monochromatic light of wavelength 500 nm is used. What will be the width of each slit for obtaining ten maxima of double slit within the central maxima of single slit pattern?

A 0.2 mm
B 0.1 mm
C 0.5 mm
D 0.02 mm

The answer is A.

Solution

Fringe width of the double slit: $\beta = \frac{\lambda D}{d}$, so ten maxima occupy $\frac{10\lambda D}{d}$.
Width of the single slit central maximum: $\frac{2\lambda D}{a}$
$\frac{10\lambda D}{d} = \frac{2\lambda D}{a} \Rightarrow a = \frac{d}{5}$
$a = \frac{1}{5}$ mm $= 0.2$ mm

Concept Fringes inside the diffraction envelope

Wave Optics in past papers

40 questions from this chapter have appeared across 18 exam years.