Question

In a double slit experiment, the slits are separated by a distance d and the screen is at a distance D from the slits. If a maximum is formed just opposite each slit, then the order of the fringe so formed is

• A. $\frac{d^2}{2\lambda d}$
• B. $\frac{2d^2}{\lambda d}$
• C. $\frac{d^2}{\lambda d}$
• D. $\frac{d^2}{4\lambda d}$

Answer 1

The correct option is A $\frac{d^2}{2\lambda d}$

$d/2\{\left|\begin{array}{ccc}....& ....& ....\\ ....& ....& ....\\ ....& ....& ....\end{array}\right|\}d$
Here $\frac{d}{2}=n\beta$
$=n\frac{D\lambda }{d}$
$\Rightarrow n=\frac{d^2}{2D\lambda }$