Question

What should the width of each slit be to
obtain 20 maxima of the double slit pattern
with in the central maximum of the single slit
pattern ? (Distance between both slit - 2
mm)

1) 0.2 mm
2) 2 mm
3) 4 mm
4) 0.6 mm​

Answer 1

Explanation:

Let a be the width of each slit. Linear separation between 10 bright fringes.

x = 10β = d10λD

corresponding angular separation

Θ1 = x/D = 10λ/d

Now, the angular width of central maximum in the diffraction pattern of a single slit,

Θ2=2λ/a

As Θ2=Θ1

2λ/a=10λ/d

or a = d/5 = 1.00/5 mm = 0.2mm