Deleted 01.curriculum/01.physics-chemistry-biology/03.Niv3/02.Geometrical-optics/05.paraxial-optics/Concept of virtual object/.gitkeep

at level 3, it is time to consider that a simple optical component can be part of an optical system, with many combined simple optical components. So the additional value compared to previous level is the concept of virtual object. So this chapter to introduce it.