Name the spherical mirror which has:(a) virtual principal focus.(b) real principal focus.

(a) a virtual principal focus is a convex mirror.

(b) a real principal focus is a concave mirror.

Explanation

A convex mirror, also known as a diverging mirror, as it is curved outward in the middle and when light strikes the reflective surface of the mirror, it diverges light rays. It has a virtual principal focus $(F)$ located behind the mirror.

It always forms virtual, erect, and diminished images irrespective of the distance between the object and the mirror.

It is used in rearview mirrors of vehicles, shop security mirrors or traffic mirrors.

A concave mirror, also known as a converging mirror, as it is curved inward in the middle and when light strikes the reflective surface of the mirror, it converges light rays. It has a real principal focus $(F)$ located in front of the mirror.

Depending on the position of the object with respect to the mirror, the types of images it forms are real, inverted as well as virtual and erect image, also the size of the images formed are magnified, diminished as well as the same size as that of the object.

It is used in solar furnaces, torches, dentist mirrors, shaving and makeup mirrors.