diff --git a/01.curriculum/01.physics-chemistry-biology/02.Niv2/04.optics/03.optical-systems-vergence/02.optical-systems-vergence-overview/cheatsheet.en.md b/01.curriculum/01.physics-chemistry-biology/02.Niv2/04.optics/03.optical-systems-vergence/02.optical-systems-vergence-overview/cheatsheet.en.md
index 4ed55e939..085bc96d7 100644
--- a/01.curriculum/01.physics-chemistry-biology/02.Niv2/04.optics/03.optical-systems-vergence/02.optical-systems-vergence-overview/cheatsheet.en.md
+++ b/01.curriculum/01.physics-chemistry-biology/02.Niv2/04.optics/03.optical-systems-vergence/02.optical-systems-vergence-overview/cheatsheet.en.md
@@ -310,6 +310,9 @@ Fig. 14.
 
 * **Emerging ray** (or its extension) = *straight line between impact point and B'*.
 
+![To find the deviation of any incident ray](rayon-incident-quelconque-2.gif)
+
+
 ##### Determining the incident ray corresponding to any emergent ray
 
 * **deflection of a ray by a thin optical element** : *local interaction the point of impact* (refraction or reflection) between  emergent ray and thin optical element $\Longrightarrow$ *independent of the distance of the image point*.