A convex lens has mean focal length of 20 cm. The dispersive power of the material of the lens is 0.02. The longitudinal chromatic aberration for an object at infinity is

A convex lens has mean focal length of 15 cm. The dispersive power of the material of prism is 0.01. What is the longitudinal chromatic aberration for the lens ?

The dispersive power of the material of lens of focal length 20cm is 0.8 . The longitudinal chromatic aberration of the lens is

An achromatic lens-doublet is formed by placing in contact a convex lens of focal length 20 cm and a concave lens of focal length 30 cm. The dispersive power of the material of the convex lens is 0.8. Determine the dispersive power of the material of the concave lens. Calculate the focal length of the lens-doublet.

An achromatic lens-doublet is formed by placing in contact a convex lens of focal length 20 cm and a concave lens of focal length 30 cm. The dispersive power of the material of the convex lens is 0.8. Determine the dispersive power of the material of the concave lens. Calculate the focal length of the lens-doublet.

Unit of longitudinal chromatic aberration of a thin lens is __________ .