Question

The distance of $n^{th}$ bright band on the screen from the central bright band on either sides of central bright band is __________.

• A. $x_n=\frac{n\lambda D}{d}$
• B. $x_n=(2n-1)\frac{\lambda D}{d}$
• C. $x_n=\frac{n\lambda d}{D}$
• D. $x_n=(2n-1)\frac{\lambda D}{2d}$

Answer 1

The correct option is A $x_n=\frac{n\lambda D}{d}$

Fringe width is $\frac{\lambda D}{d}$, which is defined as the distance between the two bright fringes.

Thus, from the center the $n^{th}$ bright fringe must be at a distance of $\frac{n\lambda D}{d}$.