What kind of mirror can have a focal length of, - 20 cm ?

Which type of mirror has :

(a) positive focal length?

(b) negative focal length?

What is the nature of a mirror having a focal length of, +10 cm ?

Complete the following sentence:

All the ______ are measured from the Pole of a spherical mirror.

What sign (+ve or -ve) has been given to the following on the basis of Cartesian Sign Convention?

(a) Height of a real image.

(b) Height of a virtual image.