In Young's double slit experiment the separation d between the slits is 2 mm, the wavelength λ of the light used is 5896 Å and distance D between the screen and slits is 100 cm. It is found that the angular width of the fringes is 0.20°. To increase the fringe angular width to 0.21° (with same λ and D) the separation between the slits needs to be changed to

Question

Question

Answer 1

CONCEPT:

Young's double experiment: In young's double-slit experiment the angular width of the fringe is written as;

Here, β is the angular width, D is the distance between screen and slits,

λ is the wavelength and d is the separation distance of the slits.

CALCULATION:

As we know that Angular width, ----(1)

Given: β 1 = 0.20°

β ₂ = 0.21°

D = 100 cm

d₁ = 2 mm

Now, On using the equation (1) we get;

----(2)

-----(3)

Now, On dividing equation (1) by equation (2) we have;

⇒

Now, On putting the given values we have,

,

∴ d₂ = 1.9 mm

Hence, Option 2) is the correct answer.