Why is an image formed where the direction of incident ray meets?For example:If a light ray is incident on a plane mirror , the ray will partly reflect and refract.Now the position where the direction of incident ray meets and a ray perpendicular to the plane mirror is where the image is formed.Why is it like that?Since the back side is polished.How does that happen we are still able to see. and please share if there is any proof or mathematical derivation for the image formation with the direction of incident ray.If you wish to close this question , please let know how this question is off-topic.