Question

How does the fringe width in a double slit interference pattern change, when the distance between the slits is increased ?

• A. Slit width decreases
  
• B. Slit width increases
  
• C. no effect
  
• D. Slits disappears
  

Answer 1

The correct option is A Slit width decreases

We know that fringe width is equal to wavelength multiplied by distance from screen to slit divided by separation of two slit

$\beta =\frac{\lambda D}{d}$

Here,

Fring width is inversely proportional to slit separation therefore, When fring width will increase than slit separation will decease.

Correct option is A.