Concave Mirror

Concave mirror is one of the types of curved mirror and concave means curved inwards. Therefore the reflecting surface is the inner curve.

What is concave mirror?

Concave mirror is also called as converging mirror, because it will converge light rays after it gets reflected. It looks like the plane mirror curved inwards and the inner curve is the reflecting surface. The good example is the inner side of a soup spoon. Basics needed to construct ray diagram of concave mirror:

• Principal axis: This is the straight line drawn through the centre of the mirror on both the side of the mirror.

• Focal point: This is the point where all the light rays converge at a single point after reflection. The length measured between the focal point and the centre of a concave mirror is considered as focal length.

• Centre of curvature: This is the point considered as the centre of the circle which is developed from the curve existed in the concave mirror. This point always lies on the point of double the focal length.

Formation of image in concave mirror:

There are different possibilities when the object is placed at the different distances from the mirror.They are:

Uses of concave mirror:

• In head light of cars : the small bulb is placed at the centre of the concave reflecting surface. The light rays got intensified due to the repeated internal reflection and send out in the form of parallel beam.
• In torches : the principle is same as that of head light.
• In solar heating devices : this device is used to heat any substance like water, food, etc with the help of sunlight. The sunlight gets converged into intensified sun light rays, so the heat energy also got multiplied and helps it to heat the substance placed on it.
• As a shaving mirror : We can use concave mirrors for shaving purpose, because it can give extensively magnified image at a particular point.