Q- An achromatic doublet consists of a biconvex positive lens of refractive index μ1 in contact with a plano concave lens of refractive index μ2. All curved surfaces have a radius of curvature R = 25 cm.
(a) If μ1red = 1.49 what is the focal length of the biconvex lens for red light?
(b) If μ2red = 1.54 what is the focal length of the plano convex lens for red light?
(c) What is the focal length of the doublet for red light?
(d) If μ1blue = 1.52 what must be the value of μ2blue for the combination to be achromatic?
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