Figure 1 shows a stepped microwave lens. Show that the surface of the Kth zone is given by r = (n - 1)f - (K -1)do n cos 0 - 1 where n is the index of refraction = ve'. Hint: At each step, the ray path length is reduced by the equivalent of a 360 change in phase delay. K =3 -K = 2 K = 1