A monochromatic light beam of wavelength ? = 698 nm is incident normally on a glass wedge with…

A monochromatic light beam of wavelength _ = 698 nm is
incident normally on a glass wedge with refractive index n = 1.50 (with respect
to the base of the wedge). Determine the angle of the wedge if the distance
between two adjacent interference minima in the reflected light is 2.0 mm.
Assume that the angle is small.