Explain with the help of a diagram, why the concave lens is also called a diverging lens.

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.

Define the principal focus of a concave lens.

Draw a ray diagram to show the formation of a real magnified image by a convex lens. (In your sketch the position of object and image with respect to the principal focus of lens should be shown clearly).