The relativistic correction to the Hydrogen Atom explained

In this video I will explain and derive the first order relativistic correction to the hydrogen atom. We will learn how to use non relativistic quantum mechanics together with perturbation theory techniques to use degenerate perturbation theory to determine the corrections to the hydrogen atom's energy levels.

In the next video we will solve an example.

My name is Nick Heumann, I am a recently graduated physicist. I love to teach physics, so I decided to give YouTube a try. English is not my first language, but I hope that you can understand me well enough regardless.
▬ Contents of this video ▬▬▬▬▬▬▬▬▬▬
00:00 Motivation
01:40 Finding formula for relativistic kinetic energy
04:45 Expanding the square root
10:00 Degenerate or non-degenerate perturbation theory?
12:20 Finding the formula