Why a convex lens called converging Iens?

Explain why a convex lens is called a converging lens.

What is the difference between a convex lens and concave lens?

If the refractive index of convex lens and surrounding medium be mu_1 and mu_2 respectively then for convex lens to act as concave lens when

A biconvex lens behaves like a convergent in air but hehaves like a divergent in water. Then refractive index (mu_L) of the lens will be -

In what condition a convex lens behave like a concave one? ,

Why are the alkanes called paraffins ?

Why are gymnosperms called conifers?

Why oxygen is called acid producer?