Question

In Young's double slit experiment, l is the wavelength of light used, d is the separation between the two slits and D is the distance of the screen from the slits. The fringe width would remain unchanged if _

• A. Both l and D are doubled
• B. Both d and D are doubled
• C. D is doubled and d is halved
• D. l is doubled and d is halved

Answer 1

Answer: (B)

Both d and D are doubled

Answer 2

Since fringe width, b = $\frac{\lambda D}{d}$

\ Fringe width b will remain unchanged, when both D and d are doubled

Therefore the answer is (2)