Question

18.
In a double-slit experiment, green light (5303 A)
falls on a double slit having a separation of 19.44
um and a width of 4.05 um. The number of bright
fringes between the first and the second diffraction
minima is :-
[JEE MAIN (Online) 2019]
(A) 04 (B) 09 (C) 05 (D) 10​

Answer 1

• The number of bright fringes between the first and the second diffraction minima is 04.

Given-

Wavelength of green light is (λ) = 5303 A⁰

Separation between the double slits is (d) = 19.44 μm

We know that angular width between second and first diffraction minima =λ/a

where a is width.

And we also know that angular width of a fringe is = λ/d

So, n=d/a = 19.44/4.05 =4

Hence number of bright fringes is 4.

Regards