Difference between Rules of reflection by mirrors and refraction by lens
Rules of reflection by mirrors
1) When an incident ray strikes on concave/convex mirrors it follows specific path after reflection. This specific path gives rise the rules for reflection due to mirror.
2) If incident ray passes parallel to principal axis, reflected ray passes through the focus.
3) If incident ray passes through focus, reflected ray passes parallel to principal axis.
4) If incident ray passes through the centre of curvature, reflected ray traces same path
5) Though in diagrams, concave mirrors are shown, but the same laws are applicable for convex mirrors too.
Rules of reflection by mirrors
1) When an incident ray strikes on concave/convex lens it follows specific path after refraction. This specific path gives rise the rules for refraction due to lenses.
2) If incident ray passes parallel to principal axis, refracted ray passes through the principal focus.
3) If incident ray passes through focus, refracted ray passes parallel to principal axis.
4) If incident ray passes through the optical centre, refracted ray traces same path.
5) Though in diagrams, convex lenses are shown, but the same laws are applicable for concave lenses too.