Spherical Mirrors
What are spherical mirrors?
As the name suggest, spherical mirrors are part of imaginary sphere as show in video below. to form a spherical mirror, part of sphere is removed and polished with shinning paint, such as silver, from one side. When the outer part of sphere is polished, it forms a concave mirror. When inner part of sphere is polished it forms convex mirror. As spherical mirrors are part of sphere, they have centre of curvature. The centre of curvature of mirrors is part of imaginary sphere out of which mirror is formed.
There are two types of spherical mirrors
Concave mirror
Convex Mirror
Principal axis of concave and convex mirrors:
Principal axis of spherical mirrors is the imaginary straight line which passes from centre of curvature and the pole of the mirrors. Principal axis in infinitely long line and extends both sides of the mirror. It helps us in calculation and to draw the image of an object formed by the mirrors. The green line in above diagrams represents principal axis.
Pole of concave and convex mirrors:
Pole is the geometric centre of the spherical mirrors. Principal axis passes form the pole. It is denoted by 'p'.
Centre of curvature:
Center of curvature is the center of sphere from which Spherical mirrors are made. A line passing from the centre of curvature is always at 90 degree from the surface of spherical mirror. It is denoted by 'C'.
Radius of curvature:
Distance between Center of curvature and the pole of spherical mirrors is called as the radius of curvature. It is denoted by R.
Focus point of concave mirror
All the rays of light traveling parallel to principal axis of a concave mirror, after reflection, meet at a point on the principal axis of the mirror. This point is called as focus point.
The distance between focus point and the pole of a convex mirror is called as focal length .
Focus point of convex mirror
The rays of light traveling parallel to principal axis of a convex mirror, after reflection, appear to meets at a point on the principal axis of the mirror. This point is called as focus point of convex mirror
The distance between focus point and the pole of a convex mirror is called as focal length .
We can note here focus point of concave mirror lies in front of the mirror and focus point of convex mirror lies behind the mirror.
