The effect on the interferences fringes in young double slit experiment if width of the slit is increased.
(A) The interference pattern gets less and less sharp
(B) The interference pattern gets brighter
(C) The interference pattern may disappear, if, condition $s/S ≤ \lambda / d$ is not satisfied. (s is size of source and S is its distance from two slits)
(D) The interference fringes becomes broad
(E) No effect on the interference pattern
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A) and (C) Only
If the slit width increases, the diffraction through each slit becomes less pronounced because the slits are no longer enough to diffract the light significantly.
Consequently, the interferance fringes become less sharp because the broader slits allow more light to pass through, reducing the contrast.
The condition $\frac{s}{S}≤\frac{λ}{d}$ ensures the light coming from the source reaches the slits in such a way that it is coherent-enough to produce a clear interference pattern.