(Advanced) The derivation of the diffraction equation depends on matching wave crests along the grating surface with openings in the grating. In the diagram at the right, the arrows indicate ray directions and the dashed lines are wave crests. Add a surface-normal line to the diagram and mark the diffracted angle on the diagram. Also sketch the right triangle sharing a hypotenuse with the grating spacing that can be used to derive the diffraction equation.

(Advanced) The derivation of the diffraction equation depends on matching wave crests along the grating surface with openings in the grating. In the diagram at the right, the arrows indicate ray directions and the dashed lines are wave crests. Add a surface-normal line to the diagram and mark the diffracted angle on the diagram. Also sketch the right triangle sharing a hypotenuse with the grating spacing that can be used to derive the diffraction equation.