Question

"In a Young’s double-slit experiment, the separation between slits is d and the screen is a distance D from the slits. D is much greater than d and λ is the wavelength of the light. The number of bright fringes per unit width on the screen is: "

A. Dd/λ
B. Dλ/d
C. D/dλ
D. λ/Dd
E. d/Dλ"

Answer 1

The number of bright fringes per unit width on the screen is,
`x=(\lambda D)/(d)`

Step-by-step explanation:

If d is the separation between slits, D is the distance between the slit and the screen and
`\lambda` is the wavelength of the light. Let x is the number of bright fringes per unit width on the screen is given by :

`x=(n\lambda D)/(d)`

`\lambda` is the wavelength

n is the order

If n = 1,

`x=(\lambda D)/(d)`

So, the the number of bright fringes per unit width on the screen is
`(\lambda D)/(d)`. Hence, the correct option is (B).