Monochromatic light with = 648 nm shines down on a plano-convex lens lying on a piece of plate glass, as shown in FIGURE 28-47.

Monochromatic light with λ = 648 nm shines down on a plano-convex lens lying on a piece of plate glass, as shown in FIGURE 28-47. When viewing from above, one sees a set of concentric dark and bright fringes, referred to as Newton's rings.

(a) If the radius of the twelfth dark ring from the center is measured to be 1.56 cm, what is the radius of curvature, R, of the lens?

(b) If light with a longer wavelength is used with this system, will the radius of the twelfth dark ring be greater than or less than 1.56 cm? Explain.

In figure 28-47

Plano-convex lens Plate glass