A mirror is a smooth surface on which regular reflection takes place. A clear image of an object placed in front of a mirror is formed due to reflection of light.
A mirror is made by giving a reflecting coating on a smooth surface. Generally a mirror is prepared by giving metal coating on one surface of glass. This process of coating with mercury or silver on glass is called silvering. Here, the surface opposite to the surface having metal coating works as the reflecting surface. Besides, surface of calm water, smooth ice etc. works as mirror.
Mirrors are mainly of two types. Namely-
- Plane mirror
- Spherical mirror
Plane mirror: If the reflecting surface is plane and smooth and regular reflection of light takes place on it, then this surface is called plane mirror. The mirror which we usually use is plane mirror.
Spherical mirror: If the reflecting surface is smooth and spherical, that means if the reflecting surface is a part of a sphere and regular reflection takes place on it, it is called spherical mirror. Spherical mirrors are shown in figures (1) and (2). If a part of a hollow glass sphere is cut off and silvering is done on one surface, then a spherical mirror is made. Again, spherical mirrors are of two types.
These are: 1. Concave mirror 2. Convex mirror
Concave mirror: If the concave surface of a sphere acts as the reflector, that is if regular reflection of light takes place from the concave surface of the spherical mirror, then it is called a concave mirror. In this case, concave mirror is made by silvering on the convex surface of the part of the sphere [figure 1]. The concave mirror is a converging mirror since the parallel beam of light converges at a point or meets together after reflection from its surface.
Fig (1) Fig(2)
Convex mirror: If the convex surface of a sphere acts as the reflector, that is if regular reflection of light takes place from the convex surface of the spherical mirror, then it is called a convex mirror. In this case, convex mirror is made by silvering on the concave or inner surface of the part of the sphere [Figure 1]. The convex mirror is a diverging mirror since the parallel beam of light diverges from a point or spreads over and never meets at a point after reflection [Figure 2].