Rules for drawing Ray Diagram in Mirrors

There are some rules which we use to obtain images in a ray diagram

Let's look at them

Rule 1 - Ray parallel to principal axis will pass through focus after reflection

For a concave mirror,

we see that ray passes through focus after reflection

For a convex mirror ,

since focus is on the right side,

it appears  that ray passes through focus after reflection

Rule 2 - Ray passing through focus will become parallel to principal axis after reflection

we see that ray passing through focus becomes parallel to principal axis after reflection

For a convex mirror,

since focus is on the right side,

it appears that ray passes through focus, and then it becomes parallel to principal axis

Rule 3 - Ray passing through Center of Curvature will follow the same path back after reflection

For a concave mirror ,

we see that ray passing through Centre of Curvature comes back the same path

For a convex mirror ,

since Center of Curvature is on the right side,

it appears that ray passes through Center of Curvature, and then it comes back along the same path

Rule 4 - Ray incident at pole is reflected back making same angle with principal axis

For both concave  and convex mirror ,

if the incident ray to the Pole makes an angle of incidence i,

then it will go back making an angle of reflection r

with Principal axis as the normal

and Angle of Incidence = Angel of Reflection