Question

In the set up shown, the two slits $S_1$ and $S_2$ are not equidistant from the slit S. The central fringe at O is then

• A. always bright
• B. always dark
• C. either dark or bright depending on the position of S
• D. neither dark nor bright

Answer 1

The correct option is C either dark or bright depending on the position of S

As the two slits $S_1$ and $S_2$ are not equidistant from the slit s the distance traversed by light through $S_1$ and $S_2$ may not differ by an integral multiple of wavelength. Thus it need not be bright . similarly it need not be dark. Thus option C is correct.