Question

In Young's double-slit experiment. If the distance between the two slits is equal to the wavelength of used light. Then the maximum number of bright fringes obtained on the screen will be

• A. Infinite
• B. $3$
• C. $7$
• D. $5$

Answer 1

Answer: (B)

We know
$dsin\theta =\pm m\lambda$
But $d=\lambda$
So $sin\theta =\pm m$
For max. $\Rightarrow sin\theta =1$
$m=\pm 1$
So maximum number of bright fringes = 3
Central maxima + either side of central maxima