Dispersive powers of materials used in lenses of an achromatic doublet are in the ratio`5:3`.If the
Channel: Doubtnut
Date: 2020-08-23

Dispersive powers of materials used in lenses of an achromatic doublet are in the ratio`5:3`.If the focal length of concave lensis `15`cm,then the focal length of the other lens will be-  `(1)=-9cm (2)+9cm (3)-12cm,(4)+12cm`