A glass `(mu=1.5)` convex lens of focl length 40 cm is placed in water `(mu=1.3)` .What will be its new focal length?

A convex lens of focal length 0.2 m and made of glass 9mu=1.50) is immersed in water 9mu=1.33) .Find the chajnge in the focal length 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) ?

The size of the image of an object,which is at infinity, as formed by a convex lens of focal length 30 cm is 2 cm. If a concave lens of focal length 20 cm is placed between the convex lens and the image at a distance of 26 cm from the convex lens, calculate the new size of the image

The radii of curvature of double convex lens are 30 cm and 60 cm and its refractive index is 1.5 .Calculate its focal length.