Question

In Young's double slit experiment the phase difference between the waves reaching the central fringe and fourth dark fringe will be

• A. $zero$
• B. $4\pi$
• C. $6\pi$
• D. $7\pi$

Answer 1

The correct option is D $7\pi$

$\Delta \varphi =(2n-1)\pi ;n=4$
$=(2\times 4-1)\pi$
$=(8-1)\pi$
$\Delta \varphi =7\pi$