Optics has as its main objective to study the nature of light and the phenomena that are related to it. In the introductory part of the study of Optics, every body that can be seen is conceptualized as a light source. Thus, light sources are bodies or objects that can receive light. They can be classified into primary (when they emit their own light) and secondary (when they reflect light that comes from other bodies).
Another very relevant subject in the study of Optics is optical systems. In Physics, a optical system as being any surface (or a set of them) that interacts directly with light. Examples of optical systems found in everyday life: the human eye, a lens, a mirror, etc.
In the study of optical systems, it is necessary to know how to differentiate object from image. For example, if you take a photograph of a car on film, you will see that only the image of the car was recorded on the film, but when we project this image onto a screen (on a screen), the car photograph is now considered as an object, since the image is seen on a screen.
Thus, an object point is a point determined by the crossing of rays that affect the considered optical system. The image point is defined as the intersection of light rays emerging from the optical system.
See the figure below: there is a representation of an optical system (S) represented by the brown bar, which can be a lens, a mirror, a flashlight, etc.
Both the object point and the image can be determined by the crossing of the rays themselves. Therefore, it is said that these are real or virtual images, as they are formed by crossing the extensions of the rays.
When the incident rays are parallel, the point is inappropriate, that is, neither real nor virtual image formation occurs. Thus, it can be concluded that long objects and images are a junction of object points and image points.
By Domitiano Marques
Graduated in Physics
Source: Brazil School - https://brasilescola.uol.com.br/fisica/definido-um-sistema-optico.htm
