Concave and Convex Spherical mirrors - Definition, Types, Uses, Image Formation, FAQs

Define Spherical Mirror.

Spherical mirror definition and spherical meaning:
A spherical mirror is any visible area that illuminates the light and produces a realistic image or virtual image. When an object is placed in front of a spherical mirror, a picture of the same object appears on the aperture of the mirror or aperture of a spherical mirror. The object is the source of the incident radiation, and the image is made up of reflected radiation. Depending on the interaction of light, images are classified as realistic or virtual imagery. The actual image occurs when the light rays meet while the virtual images appear due to the apparent difference of the light rays from the point.
Ray's drawings help us to trace the path of light so that one can see the point in the object image. Ray's drawing uses of spherical mirror lines with arrows to represent the event rays and the ray shown. It also helps us to keep track of where the light is going.

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Plane mirror vs Spherical mirrors

Plane mirror: A plane glass sheet having a thin layer of silver metal deposited on one side which is protected by a coat of red paint. The light is reflected from silvered surface of the plane mirror. A plane mirror and its schematic representation are shown in the following figure.

Spherical Mirror: It is simply a piece cut out of a glass sphere whose either of the side is made reflecting. The reflecting surface of a spherical mirror may be inwards or outwards.

Types of spherical mirrors:

There are two types of spherical mirror:

1. Concave mirror
2. Convex mirror

Concave mirror : A spherical mirror whose reflecting surface is curved inwards, facing towards the centre of the sphere is called concave mirror. It is represented by the following figure.

Convex mirror : A spherical mirror whose reflecting surface is bulging (or curved) outwards, opposite to the centre of the sphere is called convex mirror.

Characteristics of Concave Mirrors

• A concave mirror is a converging mirror.
• When the object is very close, it forms a virtual, erect, and magnified image.
• As the object is moved farther, it forms a real, inverted image (size may be smaller or larger).
• It can form both real and virtual images.

Characteristics of Convex Mirrors :

• A convex mirror is a diverging mirror it spreads light rays.
• It always forms an image that is virtual, erect, and diminished (smaller than the object).
• The image is formed behind the mirror.
• It gives a wide field of view, so it can show more area.

Image Formation by a Concave Mirror

Following table summarises the nature of image formed for different cases shown in the figures here :

Note: Concave mirror can form either real or virtual image depending on where the object is placed.

Image Formation by a Convex Mirror

Following table summarises the nature of image formed for different cases shown in the figures here :

Note : Convex mirror forms only virtual image of real object.

Uses of Spherical Mirrors

Concave mirror is used :
(i) As a reflector in search lights, head lights of motor vehicles to get powerful parallel beams of light. It is also used in telescope, solar cookers etc.
(ii) In ophthalmoscope for reflecting light on to the retina of the eye.
(iii) As a shaving mirror, make-up mirror as it can form erect and magnified image.
(iv) By dentists to see large images of the teeth of patients.

Convex mirror is used :
As rear-view mirror in automobiles (like cars, trucks and buses) to see the traffic at the back side. Such a mirror is preferred because it has a much wider field of view as compared to plane mirror or a concave mirror and always produces an erect image.

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