College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 87

A plano-convex lens with radius of curvature R = 3.0 m is in contact with a flat plate of glass. A light source and the observer's eye are both close to the normal, as shown in Figure 24.8a. The radius of the 50th bright Newton's ring is found to be 9.8 mm. What is the wavelength of the light produced by the source