Update cheatsheet.en.md

10.temporary-m3p2/16.waves/20.n2/05.waves-introduction/10.waves-in-physics/cheatsheet.en.md

@@ -143,7 +143,7 @@ _Waves generated on the water’s surface in a dish during an impact on a wall._
 ##### **Electromagnetic Waves** *($`v = c`$)*
 
 * They do not result from the disturbance of a material medium but *are formed*
-by a **perpendicular electric field and magnetic field that self-sustain**.
+by a **perpendicular electric field and magnetic field that self-sustain**.   
 <br>
 Since no supporting medium exists for electromagnetic waves, they
 **can travel through a vacuum**, including interstellar space.
@@ -164,12 +164,12 @@ Because **these waves** are **pure energy** (they have no rest mass), they are
 <br>
 At all times, **our bodies are traversed** by *radio waves*, *TV signals*, *WiFi waves* carrying
 music, images, interview speech, etc.
-**Without technology**, we would have *no awareness of most of these waves*.
+**Without technology**, we would have *no awareness of most of these waves*.   
 <br>
 
 * The **speed of electromagnetic waves** is
 always *exactly $`c = 299\,792\,458 \, \text{m/s}`$*, a fundamental constant of nature called
-*the speed of light in a vacuum*.
+*the speed of light in a vacuum*.   
 <br>
 Since this speed does not depend on the observer’s state of motion, these waves
 **defy our classical intuition** of the world. They constitute *one of the experimental proofs* of the coupling of space and time