Coming from Engineering, how difficult is it?

[deleteplease]

Hi all, I did my undergrad in Mechanical Engineering and was wondering if anybody here had experience switching to Physics/Applied Physics for a Master's. How difficult is it? Is there a lot that I have to catch up on? I have more interests in nuclear and particle physics and will probably go to school in Connecticut (since I'll be working for a company that helps pay for the tuition), so I was thinking of UConn or Yale. Any thoughts would be appreciated! 

Edited December 28, 2016 by squeegene
clarification

[Intrepid]

If you want to go more into nuclear and particle, you need to catch up on most of the junior-senior level physics classes such as EM, QM, mechanics, and statistical mechanics before you tackle the grad level courses in those respective classes along with specialization. I'm not sure what your background is, but I think that most mech e's don't require those classes.