diff --git a/contents/slides/diode_1.md b/contents/slides/diode_1.md
index 9df0031..924a8bd 100644
--- a/contents/slides/diode_1.md
+++ b/contents/slides/diode_1.md
@@ -103,9 +103,9 @@
 </right>
 
 ---
-* Berechnung: $R = \dfrac{U_q - U_{LED}}{I_D}$
+* Berechnung: $R = \dfrac{U_q - U_{\mathrm{LED}}}{I_D}$
 * $U_q$: Spannungsquelle
-* $U_{LED}$: Schwellenspannung LED
+* $U_{\mathrm{LED}}$: Schwellenspannung LED
 * $I_D$: Durchlassstrom
 
 ---