Question

Explain, how interference bands are obtained on the screen in Young's double slit experiment.​

Answer 1

Explanation:

When light waves from two illuminated slits is incident on the screen, the path traveled by each light wave is different. This path difference leads to a phase difference in the two light waves. The path difference is different for each point on the screen and hence, intensity is different for all the points. This leads to the formation and bright and dark fringes on the screen.

Consider point P on the screen as shown in the figure. 

S2P2=S2F2+PF2 

S2P=D2+(x+2d)2

Similarly,

S1P=D2+(x−2d)2

Path difference is given by:

S2P−S1P=D2+(x+2d)2−D2+(x−2d)2

Using binomial expansion,

S2P−S1P=D(1+21(Dx+2Dd)2+...)−