Question

In Young's double slit interference experiment, the wavelength of light used is $6000\dot{A}$. If the path difference between waves reaching a point P on the screen is 1.5 microns, then at that point P

• A. Second maxima occurs
• B. Second minima occurs
• C. Third minima occurs
• D. Third maxima occurs

Answer 1

The correct option is C Third minima occurs

$\lambda =6000\dot{A},x=1.5\mu m=15000\dot{A}$
For min. (dark band)
$x=(2n-1)\frac{\lambda }{2};15000=(2n-1)\frac{6000}{2}$
$15000=(2n-1)3000$
$5+1=2n$
$n=\frac{6}{2}n=3$
3rd dark band