suite update

01.curriculum/01.physics-chemistry-biology/02.Niv2/04.optics/04.use-of-basic-optical-elements/01.plane-refracting-surface/02.plane-refracting-surface-overview/cheatsheet.en.md

@@ -64,18 +64,18 @@ refracting interface corresponds to two different plane refracting surfaces :<br
 
 #### Non stigmatism of spherical refracting surfaces
 
-![](dioptre-spherique-snell-law)<br>
+![](dioptre-spherique-snell-law.png)<br>
 Fig. 3. : In each point of the spherical refracting surface, the Snell-Descartes relation applies.
 
-![](dioptre-spherique-non-stigmatique-1)<br>
+![](dioptre-spherique-non-stigmatique-1.png)<br>
 Fig. 4. : A spherical refracting surface is not stigmatic: The rays (or their extensions) coming 
 from an object point generally do not converge towards an image point.
 
-![](dioptre-spherique-non-stigmatique-2)<br>
+![](dioptre-spherique-non-stigmatique-2.png)<br>
 Fig. 5a. : If we limit the opening of the spherical refracting surface so that only the rays 
 meeting the surface near the vertex are refracted through the surface.
 
-![](dioptre-spherique-gauss-conditions)<br>
+![](dioptre-spherique-gauss-conditions.png)<br>
 Fig. 5b. : and if the object points remain close to the optical axis, so that the angles of 
 incidence and refraction remain small, then for each object point an image point can be almost
 defined, and therefore the spherical refracting surface becomes quasi-stigmatic.