M.Sc Physics

Hello Govind,
Yes, you can. Most universities require you to have physics as your extra-departmental/pass course for you to study physics in M.Sc. However, since science departments offer admission to Master's degree students via entrance exams, this might be difficult anyway. You'll have to work hard in physics to crack entrance exams. Alternatively, you could apply for an applied mathematics degree in Calcutta University or CMI or even for M.Sc in mathematics. Most of the departments have someone or the other working in the mathematical physics. Courses that are relevant to that are differential geometry, probability theory/functional analysis, representation theory/Lie groups and of course, the theory of differential equations.
Approaching physics via mathematics is reasonably common.