Rules For Image Formation From Concave Mirror (a) When the light ray incident parallel to the principal axis.
OR
When the light ray incident parallel to the principal axis.
(b) When the light ray incident on the mirror directing towards centre of curvature.
SIGN CONVENTION (a)
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 :
1. All distances are measured from the
pole of the mirror.
2. The distances measured in the
same direction as the direction of incident light from pole are taken as
positive.
3. The distances measured in the direction
opposite to the direction on incident light from pole are taken as
negative.
4. Distances measured
upward and perpendicular to the principal axis, are taken as
positive.
5. Distances measured
downward and perpendicular to the principal axis, are taken as
negative.