---
title: 'The physical object that diffuses the light'
slug: ray-tracing
---

#### course to build

<!-- ideas :

1) "diffused light" , correct ? , i want to say light that has undergone "specular reflexion" or "diffuse reflection". I am not sure the word "scattering" or "scattered light" apply exactly in this particular case of specular reflexion... (?) To check (Rayleight scattering by homogeneous spheres seems to me different)

2) it is important to tell about extended real sources that diffuse the light, then to consider each infinitesimal surface of the extended object, notion of point source that diffuse the light, and the characteristics of each point sources : all rays emmitted by these point sources originate from the point sources, diverge from the point source. This will be too the characteristic of a point object in geometrical optics.
In this sense : all point source is a point object, but point objects are not all point sources.
Must be clear for student.

-->
