If a mirror is obtained from a sphere silvered on the outer side, it is called a concave mirror
If a mirror is obtained from a sphere silvered inside, it is called a convex mirror
Terms relating to spherical mirrors
Length MM’ is the measure of aperture, C is the centre of curvature, P is the pole, and PC is the principal axis.
The portion available for reflection is called aperture; MPM’ is the aperture.
It is the geometric centre of the reflecting surface. P is the pole.
Centre of curvature
It is the centre of the sphere of which the mirror forms a part. C is the centre of curvature.
It is the straight line passing through the centre of curvature and the pole.The line passing through P and C in the figure is the principal axis.
Radius of curvature (R)
It is the radius of the sphere of which the mirror forms a part. PC is the radius of curvature.
In case of the concave mirror, the parallel beam after reflection converges at a point F called the principal focus.
In case of a convex mirror,it appears to diverge from a point F called the focus
It is the distance between the pole and the principal focus.PF is the focal length. Focal length is measured in m or cm. for a spherical mirror, the radius of curvature is twice its focal length.
The rear view mirror of a car is a plane mirror. A driver is reversing his car at a speed of 2 m/s. The driver sees in his rear view mirror, the image of a truck parked behind his car. The speed at which the image of the truck appears to approach the driver will be : (a) 1 m/s (b) 2 m/s (c) 4 m/s (d) 8 m/s
Formation of image by concave mirror
AB is an extended object and A1B1 is an image formed by the concave mirror of small aperture
When a lighted bulb is placed at the focus of a concave mirror reflector, the diverging light rays of the bulb are collected by the concave reflector and then reflected to produce a strong, parallel-sided beam of light
Uses of Concave Mirrors
Concave mirrors are used as shaving mirrorsto see a large image of the face.
Concave mirrors are used by dentists to see the large images of the teeth of patients.
Concave mirrors are used as reflectors in torches, vehicle head-lights and search lights to get powerful beams of light
Large concave mirrors are used in the field of solar energy to focus sun’s rays for heating solar furnaces.
Formation of image by convex mirror
Uses Of Convex Mirror
Image formation by a Convex Mirror used as rear-view (wing) mirrors in vehicles.
These mirrors are fitted on the sides of the vehicle, enabling the driver to see traffic behind him/her to facilitate safe driving.
Convex mirrors are preferred because they always give an erect, though diminished, image.
Also, they have a wider field of view as they are curved outwards. Thus, convex mirrors enable the driver to view much larger area than would be possible with a plane mirror.