Question

how can we say that the point size image formed on the concave mirror at focus is inverted?

Answer 1

As you can see in the above image that spherical Mirrors are of two types ---- first is concave mirror and second is convex mirror. Now I will tell you more about concave mirror. A spherical mirror whose refleccting surface is depressed and generally makes inverted is called concave mirror. The images formed in this mirror may be real or virtual. The example is the inner surface of the spoon hand shaving mirror .

Answer 2

Explanation:

If the object is placed at infinity then the light rays from it are parallel to principle axis of the concave mirror. if the light ray parallel to principle axis then all the light rays refract and join at the focus