Principal focal point – Convex mirror

The most important characteristic of a convex mirror is its principal focal point. 

We know the term principal and this gives you a clue that there is a point on the principal axis where parallel rays will look like they have diverged away from a focal point that is behind the mirror.

But be careful because this only applies to light that is passing parallel to the principal axis.

Only the light ray hitting the mirror along the principal axis will bounce back in the exact opposite direction.

The principal focus does not mean that an image is focused at this point, it only means it is a point where parallel rays appear to pass through. Call it the principal focal point.