Newton's rings in transmitted and reflected white light

In the experiment P5.3.3.2, the Newton’s rings are studied both in reflection and in transmitted light. As the partial beams in the air wedge are shifted in phase by λ/2 for each reflection at the glass surfaces, the interference conditions for reflection and transmitted light are complementary. The radii r_n of the bright interference lines calculated for transmitted light using the equations above correspond precisely to the radii of the dark rings in reflection. In particular, the center of the Newton’s rings is bright in transmitted light and dark in reflection. As white light is used, the interference rings are bordered by colored fringes.