The focal length of a convex lens for red and violet colours is 26 cm and 25 cm respectively. Find dispersive power of the lens.

A parallel beam of white ligth falls on a convex lens .Images of blue ,yellow nd red ligth are formed on the other side of the lens at distnaces 20 cm,20.5 cm and 21.4 cm respectively.The dispersive power of the material of the lens is

If f_v and f_r are the focal lengths of a convex lens fro violet and red light respectively and F_v and F_r are the respective focal length of a concave lens,then we must have

The focal length of a coverging lens is measured for violet,green and red colours.It is f_v,f_g and f_r respectively.We will get

The radii of curvature of the faces of a double convex lens are 10 cm and 12 cm respectively.If the focal length of the lens is 12 cm ,find the refractive index of the material of the lens.

The focal length of a concavo - convex lens of radii of curvature 5 cm and 10 cm is 20 cm.What will be its focal length in water (mu=4//3) ?

Find the focal length of a lens of power- 2.0 D.What type of lens this?

The radius of curvture of the convex face of a plano-covex lens is 12 cm and its refractive index is 1.5. Find the focal length of the lens. .

If the focal length of a converging lens is 50 cm. What is the power of the Lens ?