Two lenses having `f_(1):f_(2)=2:3` has combination to make no dispersion. Find the ratio of dispersive power of glasses used

An achromatic convergent lens of focal length 150 cm is made by combining flint and crown glass lenses. Calculate the focal length of both the lenses and point out which one is divergent if the ratio of the dispersive power of flint and crown glasses is 3:2.

An achromatic convergent lens of focal length 150 cm is made by combining flint and crown glass lenses. Calculate the focal length of both the lenses and point out which one is divergent if the ratio of the dispersive power of flint and crown glasses is 3:2.

Two prisms A and B are in contact with each other have angular dispersions of 2^(@) and 4^(@) respectively. The dispersive power of A is 0.002. If the combination produces dispersion without deviation, the dispersive power of B is

Two prisms A and B are in contact with each other have angular dispersions of 2^(@) and 4^(@) respectively. The dispersive power of A is 0.002. If the combination produces dispersion without deviation, the dispersive power of B is

Two lenses in contact form an achromatic lens. Their focal lengths are in the ratio 2 : 3 . Their dispersive powers must be in ratio of