Light 4

Characteristics of images formed in a plane mirror :
1. Size of the image is always equal to the size of the object. Hence, its magnification is unity.
2. The image formed is laterally inverted. When you stand in front of the mirror, your right hand appears left and your left hand appears right.
3. The image formed is as far behind the mirror as the object is in front of it. The image distance is equal to the object distance.

If the mirrors are not plane surfaces then they are called spherical mirrors. There can be two types of spherical mirrors : Concave and Convex.
Few definitions related to spherical mirrors are :
1. Centre of curvature: The centre of an imaginary sphere of which the mirror is a part.
2. Radius of curvature : The radius of the hollow imaginary sphere of which the mirror is a part. It is denoted by R.
3.Pole : The central point of the spherical mirror.
4. Focus : When parallel beam of light is incident on a spherical mirror, then after reflection the rays meet at this point in case of concave mirror, and appear to diverge out from the point in case of a convex mirror, then that point is called the Focus.
5. Focal Length : The distance between the pole and the focus is called focal length. Generally, it is denoted by f , and the relation f = R/2 always holds true.
6. Magnification : The ratio of the size of the image to the size of the object is called magnification. It is denoted by m.

Light 3 - Reflection

The phenomenon of rebouncing of light rays into the same mediumon striking a surface is called Reflection of light.

Laws of Reflection
Following are the two laws of reflection of light:
1. The incident ray, the reflected ray and the normal at the point of incidence all lies in the same plane.
2. The angle of incidence is always equal to the angle of reflection at the point of incidence.

Angle of incidence : It is the angle which the incident ray makes with the normal at the point of incidence.
Angle of Reflection : It is the angle which the reflected ray makes with the normal at the point of incidence.

Types of Reflection :
1. Regular Reflection : When a parallel beam of reflected light rays is obtained when parallel light rays are incident on a smooth reflecting surface, then that is called Regular Reflection.
Example: Light rays falling on a mirror gets reflected back.
2. Irregular or Diffused Reflection : When a non-parallel beam of reflected rays are obtained when parallel incident light rays fall on an uneven surface , then that is called Irregular or Diffused Reflection.
Example: Light rays falling on a wall.

Note: The Laws of Reflection holds true for both regular and irregular reflection. Incase of irregular reflection, however, the laws hold true for each point of the incident beam of light.