A plane light wave with wavelength λ = 0.50 μm falls normally on the face of a glass wedge with an angle θ = 30°. On the opposite face of the wedge a transparent diffraction grating with ** d = 2.00 μm is inscribed, whose lines are parallel to the wedge'* edge. Find the angles that the direction of incident light forms with the directions to the principal Fraunhofer maxima of the zero and the first order. What is the highest order of the spectrum? At what angle to the direction of incident light is it observed?
The diffraction formula is easily obtained on taking account of the fact that the optical path in the glass wedge acquires a factor n (refractive index). We get
We calculate θk for various k by the above formula. For k = 6.
