What is a lens? Distinguish between a convex lens and a concave lens. Which of the two is a converging lens: convex lens or concave lens?

State any two uses of convex lenses.

Fill in the following blanks with suitable words:

(a) _______ rays of light are refracted by a convex lens to a point called the focus.

(b) The image in a convex lens depends upon the distance of the object from the______.

Explain with the help of a diagram, why the convex lens is also called a converging lens.

Define principal axis, principal focus and focal length of a convex lens.