Main Question or Discussion Point
What are the specializations in physics that I can choose in graduate school? Aside from Theoretical Physics, Astrophysics, Particle Physics, Medical Physics... What else?
On principle you should know your relevant theory as an experimentalist but picking an applied field you will not really "do" much theory. I spent the years of of my PhD in the lab, tinkering with devices, repairing stuff, working with the guys in the workshop to have my apparatuses built etc.As I understand it, all the branches of physics have a theoretical aspect.