Two lenses in contact made of materials with dispersive powers in the ratio`2:1`behaves as ab achromatic lens of focal length `10cm`.The individual focal length of the lenses are :

The dispersive powers of the materials of the two lenses are in the ratio 4:3 .If the combination of these two lenses is of focal length 60 cm,then the focal lengths of the component lenses are:

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 ?

Two convex lenses of focal length 10 cm each are combined. What will be the focal length of the combined lens ?

Two thin lenses are in contact with each other. One of these is a concave lens of focal length 20 cm and the other is a convex lens of same focal length of the combination and state how it behaves.

A convex lens of focal length 10 cm is placed in contact with a concave lens of focal length 20 cm. The focal length of this combination of lenses will be: