# Light

## 03 Spherical Mirror

#### 3.1TERMINOLOGIESOF SPHERICAL MIRRORS

(i)Centre Of Curvature: It is the Centre of the hollow sphere of glass of which the mirror is a part.(ii)Radius Of Curvature:It is the radius of the hollow sphere of glass of which the mirror is a part.

(iii) Pole: It is the centre of a spherical mirror.
(iv)Principle Axis:It is the straight line passing through the centre of curvature and pole of a spherical mirror.
(v)Aperture Of The Mirror: The portion of a mirror from which the reflection of light actually takes place.
(vi)Linear Aperture: It is the diameter of the circular boundary of the mirror.

(vii)Angular aperture: The angle subtended by the circular boundary of the mirror is called its ‘angular aperture’.

#### 3.2 TYPES OF SPHERICAL MIRRORS

It is a form of electromagnetic radiation (radiant energy) which makes objects visible. When the light ray falls on an object, it is reflected back and enters our eyes. This produces sensation of vision.

The types of spherical mirror are:

(i) Concave Mirroror converging mirror
(ii) Convex Mirror or diverging mirror

(i)A concave mirror is aspherical mirror in which the reflection of light takes place at the concave surface (or bent-in surface or inner hollow surface). The rays of light converge after being incident on a concave mirror.

(ii) A convex mirror is aspherical mirror in which the reflection of light takes place at the convex surface(or outer bulged surface).The rays of light diverge after being incident on a concave mirror.

#### 3.3 CONCAVE MIRROR: TERMINOLOGIES

Principal focus: It is a point on its principal axis to which all the light rays which are parallel and close to the axis, converge after reflection from the concave mirror.

Focus: The focus of a concave mirror is in front of the mirror.

Focal length:The focal length of a concave mirror is the distance between its pole and principal focus.

#### 3.4 Convex Mirror: TERMINOLOGIES

Principal Focus: It is a point on its principal axis from which a beam of light rays, initially parallel to the axis, appears to diverge after being reflected from the convex mirror.

#### 3.5 RELATION BETWEEN RADIUS OF CURVATURE AND FOCAL LENGTH OF A SPHERICAL MIRROR

The focal length f of a spherical mirror is half of its radius of curvature R. It is represented as:

Thus, the principle focus of a spherical mirror lies midway between the pole and the centre of curvature.