The dispersive powers of glasses of lenses used in an achromatic pair are in the ratio 5 : 3. If the focal length of the concave lens is 15 cm , then the nature and focal length of the other lens would be

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

The dispersive powers of the materials of two lenses forming an achromatic combination are in the ratio of 4:3 . Effective focal length of the two lenses is + 60 cm then the focal lengths of the lenses should be

A comvex lens and a concave lens are placed in contact. The ratio of magnitude of the power of the convex lens to that of the concave lens is 4:3. If the focal length of the convex lens is 12 cm, then the focal length of the combination will be

A comvex lens and a concave lens are placed in contact. The ratio of magnitude of the power of the convex lens to that of the concave lens is 4:3. If the focal length of the convex lens is 12 cm, then the focal length of the combination will be

The dispersive powers of crown and flint glasses are 0.02 and 0.04 respectively. In an achromatic combination of lenses the focal length of flint glass lens is 40 cm . The focal length of crown glass lens will be

The dispersive powers of the materials of convex lens and concave lens placed in contact are in the ratio 1 : 2. For the achromatic combination, we take convex lens of focal length 100 cm. What should be the focal length of concave lens ?

The dispersive powers of two lenses are 0.01 and 0.02 . If focal length of first lens is +10cm , then what should be the focal length of the second lens, so that they form an achromatic combination ?