Hello.
Choice of MSc in any of the stream depends upon your interest , if you are confused then try to see in yourself and find your interest and find in which subject you never feel exhausted , anytime anywhere if you have to work on it then you feel ready , if you fee it is physics then there will be no problem, doing MSc in physics would not be tough if your determination to do it is strong enough and your full interest is toward it, after this you still have many opportunities and even opportunities will come by itself if you have strong skills.
Best of luck.