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Mirrors
When a ray of light falls on a surface, then it can undergo one of the following three phenomena:
When it falls on a normal surface then most of the light gets absorbed.
A mirror is an object that reflects the light in the same angle as it receives from the object. Mirrors are polished surfaces coated with mercury such that they reflect most of the light falling on them to form a clear image .
Images can be of two types: Real image and Virtual image. An image that can be formed on the screen is known as a real image and the one which cannot be formed on the screen is known as a virtual image. These images are formed when light falls on a mirror from the object and is reflected back by the mirror on the screen.
There can be two types of mirror: Curved mirror and plane mirror. If a curved mirror is a part of a sphere then it is known as a spherical mirror. The image formed by a plane mirror is always a virtual image as it cannot be obtained on a screen. The image formed by the spherical mirror can be either real or virtual.
Spherical mirrors are of two types:
- Convex mirrors
- Concave mirrors
So to form an image we require at least two rays from the object which meet or appear to meet at a point. In the case of a plane mirror, here we have used three images for better clarity in the ray diagram shown below.
For the ray starting from point A and travelling in a horizontal direction towards point E, the angle of incidence is 0 and hence it retraces its path. Similarly, the ray starting from A and travelling towards point C follows the law of reflection. When these rays are produced backwards they appear to meet at a point E and D. Now this image is known as a virtual image.
In real image, the rays of light actually meet after reflection while in a virtual image it appears to meet but not actually meet. A real image can be obtained on screen but not a virtual image.
Characteristics of the image formed by a plane mirror :
- It is virtual
- It is erect and of the same size as the object
- The distance of the object from the plane mirror is the same as the distance of the image from the plane mirror.
One of the important characteristics of the image is that it is laterally inverted. It means if you raise your left hand it would appear in the plane mirror that you have raised your right hand.