Question

The imaginary line passing through the pole and the center of curvature of the curved mirror is called its ………………….
A) Focal length
B) Radius of curvature
C) Principal axis
D) None

Answer 1

Hint: The above problem is based on the terminologies of the optics of the curved mirror. The focal length, radius of curvature and principal axis are the terminologies that describe the curved mirror. The size of the image formed varies according to these terminologies.

Complete step by step answer:
The incident rays after converging or diverging become concentrated at a point. This point is called the focus of the curved mirror. The distance of the focus from the pole of the curved mirror is called the focal length of the curved mirror, so the option (A) is incorrect.
The curved mirrors are formed by cutting a piece from the spherical mirror. The radius of the spherical mirror from which the curved mirror formed is called the radius of curvature, so the option (B) is incorrect.
The center of the spherical mirror that forms the curved mirror is called the center of curvature. The center of the aperture of the curved mirror is called the pole of the curved mirror. The imaginary line that joins the pole to the curved mirror to the center of curvature of the curved mirror is called the principal axis.

Thus, the option (C) is the correct answer of the problem.

Additional Information: The point at which the rays appear to meet or appear to come out is called the principal focus of the curved mirror. It lies between the center of curvature and pole of the curved mirror.

Note: The principal focus, center of curvature and pole of the curved mirror lies on the principal axis of the curved mirror. The principal focus of the curved mirror always remains at the same distance from the pole and center of curvature of the curved mirror.