Question

Assertion :In Young's experiment, the fringe width for dark fringes is different from that for white fringes. Reason: In Young's double-slit experiment, when the fringes are observed with a source of white light, then only black and bright fringes are observed.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is D Assertion is incorrect but Reason is correct

Both dark and bright fringes have width equal to $\beta =\frac{D\lambda }{d}$. Hence assertion is incorrect.

While the reason statement is correct, the central fringe is white and all other fringes are coloured when white light is used as a source.