Question

In the arrangement shown L₁ ,L₂ are slits and S₁ , S₂ two independent sources on the screen, interference fringes

(a)  will not be there

(b)  will not be there if the intensity of light reaching the screen from S₁ and S₂ are equal.

(c)  will be there under all circumstances

(d)  we will have only the central fringe

Answer 1

Correct option  (b) will not be there if the intensity of light reaching the screen from S₁ and S₂ are equal.

Explanation:

On the screen, we have four amplitudes pair wise coherent.

(A₁ + A₂) + (A₃ + A₄) = A₁₂ + A₃₄

However, If A₁₂ and A₃₄ have equal magnitude because of random phase of A₁₂ and A₃₄, no fringes will be seen.