In a Young's double-slit interference apparatus,by what factor is the distance between adjacent light and dark fringes changed when the separation between slits is tripled?
A)1/9
B)1/3
C)1
D)3
E)9

Question

In a Young's double-slit interference apparatus,by what factor is the distance between adjacent light and dark fringes changed when the separation between slits is tripled?
A)1/9
B)1/3
C)1
D)3
E)​9

Quizplus · Accepted Answer

The distance between adjacent bright and dark fringes in Young's double-slit interference apparatus is given by:

D = λL/d

where λ is the wavelength of light, L is the distance between the slits and the screen, and d is the separation between the slits.

If the separation between the slits is tripled (d' = 3d), then the distance between adjacent bright and dark fringes becomes:

D' = λL/d'

D' / D = d / d'

= d / 3d

= 1/3

Therefore, the distance between adjacent fringes is decreased by a factor of 1/3 when the separation between the slits is tripled. So, the correct choice is B.

In a Young's Double-Slit Interference Apparatus,by What Factor Is the Distance