Question

In a double-slit experiment, green light (5303 Å) falls on a double slit having a separation of 19.44μm and a width of 4.05μm. The number of bright fringes between the first and the second diffraction minima is :

Answer 1

Answer:

5 bright fringes

For diffraction :

Location of 1st minima

y1=Dλ/a=0.2469Dλ

Location of 2nd minima  

y2=2Dλ/a=0.4938Dλ

Now for interference :

Path difference at P.

dy/D=4.8 λ

Path difference at P.

dy/D=9.6λ

So orders of maxima in between P and Q is

5, 6, 7, 8, 9

So 5 bright fringes are present between P and Q.

Hope this answer helped you :)