Question

A student performs a double-slit interference experiment. The student records the fact that a third-order dark fringe is located at an angle of 15o for a given light source. The wavelength of light is then decreased by 30.0nm, and the student records the fact that the second-order dark fringe is now located at an angle of 10o . What is the slit distance?

Answer 1

Sol: Here

or

If slit distance is d then condition for minima

Hence

or

or

and

or

by solving equation (2) and (3)

we get

d=9518 nm  

or