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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

@@ -128,8 +128,8 @@ We call **thin spherical refracting surface** a spherical refracting surface *us
 which defines $`\overline{SC}`$ : algebraic distance between vertex S and center C of curvature on optical axis.
 
 * 2 refractive index values :<br>
-\- **$`n-{inc}`$ : refractive index of the medium of the incident light**.<br>
-\- **$`n-{eme}`$ : refractive index of the medium of the emergent light**.
+\- **$`n_{inc}`$ : refractive index of the medium of the incident light**.<br>
+\- **$`n_{eme}`$ : refractive index of the medium of the emergent light**.
 
 * 1 arrow : indicates the *direction of light propagation*
 * 
@@ -145,7 +145,7 @@ which defines $`\overline{SC}`$ : algebraic distance between vertex S and center
 * **Transverse magnification expression**<br><br>
  **$`\overline{M_T}=\dfrac{n_{inc}\cdot\overline{SA_{ima}}}{n_{eme}\cdot\overline{SA_{obj}}}`$**&nbsp;&nbsp;  (equ.2)
 
-You know $`\overline{SA_{obj}}$, $n_{inc}$ and $n_{eme}`$, you have previously calculated $`\overline{SA_{ima}}`$, so you can calculate $`\overline{M_T}`$ and deduced $`\overline{A_{ima}B_{ima}}`$.
+You know $`\overline{SA_{obj}}`$, $`n_{inc}`$ and $`n_{eme}`$, you have previously calculated $`\overline{SA_{ima}}`$, so you can calculate $`\overline{M_T}`$ and deduced $`\overline{A_{ima}B_{ima}}`$.
 
 
 ! *USEFUL* : The conjuction equation and the transverse magnification equation for a plane refracting surface are obtained by rewriting these equations for a spherical refracting surface in the limit when $`|\overline{SC}|\longrightarrow\infty`$.<br> Then we get *for a plane refracting surface :*