Sign Convention for Spherical Mirrors
1. All distances are measured from the pole of the mirror. 2. Distances measured in the direction of incident light rays are taken as positive. 3. Distances measured in opposite direction to the incident light rays are taken as negative. 4. Distances measured above the principal axis are positive. 5. Distances measured below the principal axis are negative.
Lateral inversion
In the image formed by a plane mirror the right side of the object ppears as left side and vise-versa. This phenomena is called lateral inversion.
When object is placed between pole and focus of a concave mirror, then its virtual, erect and magnified image is formed.
A convex mirror forms a virtual, erect and diminished image for all conditions of object.
The focal length of concave mirror is taken negative and for a convex mirror taken as positive.
Refraction of Light
The deviation of light rays from its path when it travels from one transparent medium to another transparent medium, is called refraction of light.