An achromatic lens -double is formed by in contact a convex lens of focal length 20 cm
Channel: Doubtnut
Date: 2020-08-30

An achromatic lens -double is formed by in contact a convex lens of focal length 20 cm amd a concave lens of focal length 30 cm.The dispersive of the meterial of the convex lens is 0.18  (a) Determine the dispersive power of the meterial of the concave lens (b) Calculate the focal of the lens-doublet 0.27 (b) 60 cm