Under what conditions a concave lens can behave as a converging lens?

How can a convex lens behavae like a diverging lens?

Under what conditions will a convex lens have a negative and a concave lens a positive power?

under what condition does a biconvex lens of glass having a certain refractive index act as a plane glass sheet,when immersed in a liquid?

Why does a convex lens of glass mu=1.5 behave as a diverging lens when immersed in carbon disulphide of higher refractive index mu=1.65 ?

Can a convex (converging) lens behave as concave (diverging) lens in some situations? Give example?

A convex lens becomes less converging when placed in

A biconvex lens of a transparent material of refractive index 1.25 is immersed in water of refractive index 1.33 will the lens behave as a converging or a diverging lens?Give reason.