Rules for Image Formation by Ray Diagram
Rules for image formation from concave mirror
When the light ray incident parallel to the principal axis.
OR
When the light ray incident towards focus.
When the light ray incident on the pole of the mirror.
Read Also : Important Rule of Light Reflection
Rules for image formation from convex mirror
When the light ray incident parallel to the principal axis.
OR
When the light ray incident parallel to the principal axis
When the light ray incident on the mirror directing towards centre of curvature.
Sign convention
Description : It is a convention which fixes the signs of different distances measured. The sign convention to be followed is the New Cartesian sign convention. It gives the following rules :
- All distances are measured from the pole of the mirror.
- The distances measured in the same direction as the direction of incident light from pole are taken as positive.
- The distances measured in the direction opposite to the direction on incident light from pole are taken as negative.
- Distances measured upward and perpendicular to the principal axis, are taken as positive.
- Distances measured downward and perpendicular to the principal axis, are taken as negative.
Read Also : Reflection from Spherical Mirror