In Young's double-slit experiment, the fringe width $w$ is given by:
A$w = \lambda d / D$
B$w = \lambda D / d$
C$w = D / (\lambda d)$
D$w = (\lambda + D)/d$
Answer & Solution
Correct answer: B. $w = \lambda D / d$
Fringe width (separation between adjacent maxima or minima) $w = \lambda D/d$, where $D$ = screen-slit distance, $d$ = slit separation, $\lambda$ = wavelength. Bigger $\lambda$ or $D$, or smaller $d$ ⇒ wider fringes.
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