Question

In interference pattern, using two coherent source of light the fringe width is .....
A)directly propotional to wevelenght
B)inversely proportional to sq. of the wevength
C)inversely proportional to wevelenght
D) directely propotional to sq. of the wevelength

Answer 1

a option dear
hope it was helpful dear

Answer 2

Answer : fringe width is directly proportional to wavelength .

Explanation :- as you know , fringe width is the separation between two consecutive bright or consecutive dark .
We know, for bright , yn = nλD/d ,
And for dark , yn = (2n-1)λD/d
Here, λ is wavelength of wave , d is the separation between slits and D is the separation between slit and screen.

Now, fringe width = Y₂ - Y₁ = 2λD/d - λD/d = λD/d [ when we take bright ]
also fringe width is same for dark = 3λD/2d - λD/2d = λD/d

Finally, fringe width = λD/d , hence, fringe width is directly proportional to wavelength.