Lag1989 task №20.20

A flat-convex lens is placed on the glass plate with the convex side. With a normal incidence of red light on the flat boundary of the lens (λ = 610 nm), the radius of the fifth bright Newton’s ring is r₅ = 5 mm. Find: a) the radius of curvature R of the convex boundary of the lens; b) the optical power f of the lens, if the refractive index of the lens is n = 1.5; consider the lens thin; c) the radius of the third bright ring r₅. Observation is conducted in reflected light.