Lars kleyn Winkel
--- a/src/7_tight_binding_model_sol.md

+ 1

− 1
+++ b/src/7_tight_binding_model_sol.md

+ 1

− 1
 @@ -52,5 +52,5 @@ pyplot.yticks([0.5, 1], [0, r'$\frac{L}{2\pi a}\sqrt{\frac{\kappa}{m}}$'])

 4.

-
+Hint: The group velocity is inversely proportional