Spherical mirrors are mirrors with curved surfaces that are shaped like a section of a sphere. These mirrors have many applications, including in telescopes, microscopes, cameras, and many other optical devices. They are commonly used to reflect light and form images of objects.
Types of Spherical Mirror
They come in two main types:
- Convex Mirror or Diverging mirror :- In convex mirror the reflective surface bulges outwards, away from the center of the sphere. This type of mirror is also known as a diverging mirror, as it diverges light rays that are incident upon it.
- Concave Mirror or Converging mirror :- In concave mirror the reflective surface curves inward, towards the center of the sphere. This type of mirror is also known as a converging mirror, as it converges light rays that are incident upon it.
(1) Pole/vertex (P) :- Pole is the mid point of a spherical mirror.
(2) Center of curvature (C) :- The center of curvature is the center of the sphere of which the spherical mirror is a part.
(3) Principal Axis:- The principal axis is an imaginary line passing through the pole and center of curvature.
(4) Principal focus:- The principal focus is a point on the principal axis where a ray of light incident parallel to the principal axis, after reflection from the spherical mirror, actually meets (concave mirror) or appears to meet (convex mirror).
(5) Focal Length:- The focal length is the linear distance between the pole and the principal focus.
(6) Radius of curvature :- Radius of curvature is the linear distance between pole and center of curvature.
(7) Aperture :- The diameter of the reflecting surface of a spherical mirror is called its aperture (aa’ and bb’ in the above figure).
(8) Focal Plane:- The plane passing through the focus and perpendicular to the principal axis is called focal plane.
(9) Paraxial Rays: – These rays make a small angle with the normal at the point of incidence and are therefore close to the principal axis.
(10) Marginal rays: – The angle of incidence of these rays is large.