Question

Define the pole, the center of curvature, the radius of curvature, principal axis, aperture, focus, and focal length of a spherical mirror.

Answer 1

1. A spherical mirror is a mirror that has the shape of a piece cut out of a spherical surface.
2. There are two types of spherical mirrors: concave mirror and convex mirror.
3. A concave mirror is one whose reflecting surface is towards the centre of the sphere of which the mirror is a part.
4. A convex mirror is the one whose reflecting surface is away from the centre of which the mirror is a part.
5. Pole: It is the geometrical centre of the reflecting surface. It is represented by the letter P.
6. Centre of curvature: It is the centre of the sphere of which the mirror forms the part. It is represented by C.
7. The radius of curvature: It is the radius of the sphere of which the mirror forms the part. It is represented by R. $PC=R$
8. Principal axis: The straight line joining the pole (P) and the centre of curvature. It is normal for the mirror at its pole.
9. Aperture: The diameter of the spherical mirror is called its aperture. It represents the reflecting surface of the mirror.
10. Focus: It is the point of the principal axis at which the rays parallel to the principal axis meet (concave mirror) or appear to meet (convex mirror) after reflection. It is represented by F.
11. Focal Length: The distance between the pole and the principal focus of a spherical mirror is called the focal length. It is represented by f.$focallength,f=PF$.