Until then, the debate was whether light is some sort of wave or instead it consists of material particles bouncing around after being emitted from a light source. The difference between mirror-like and regular surfaces is that the surface of a mirror is extremely smooth and uniform, so that a bunch of rays hitting it will retain their relative orientation after reflection. In ordinary surfaces instead, the direction of a reflected ray is practically unpredictable, since the surface irregularities do not allow to define a precise direction for the normal to the surface. Having clarified this, from now on we will just deal with smooth, specular, perfectly reflecting surfaces.
Plane mirrors can only have virtual images, to get a real image one needs curved mirrors.
You don't need to remember this. This property is exploited in your car's headlights, your TV satellite dish, etc. In most applications, instead of parabolic mirrors one can use spherical mirrors since in a spherical mirror light rays almost have the same property of focus convergency, as long as they are not very far from the mirror's axis. In other words, if f is the focal distance . Based on this knowledge, we can determine the response of a spherical mirror to objects positioned at different locations.