Question

in YDSE, 10 fringes are observed to be formed in a certain segment of the screen when light of wavelength 400nm is used. if the wave length of light is changed to 200nm, the number of fringes observed in the same segment of the screen is?

Answer 1

On the same segment you will get 20 fringes, the double. But the intensity (energie) of fringe light decreases with the increase of fringes.

The decrease of energie is express by this factor :
\[\sin ^{2}(\pi.l.x/(\lambda.D))\]
D : distance between screan and source
\[\lambda\]: wavelenght
l : slot width