A laser of wavelength 720 nm illuminates a double slit where the separation between the slits is 0.22 mm. Fringes are seen on a screen 0.85 m away from the slits. How far apart are the second and third bright fringes

The appropriate solution is "2.78 mm".

Explanation:

Given:

or,

or,

As we know,

Fringe width is:

⇒

hence,

Separation between second and third bright fringes will be:

⇒

or,

if you already have the answer to (a), then just work out how many periods there are in 1 minute, and that's the answer to (c).

i think the answer would be reserve.