I think the reason for opting geography instead of physics is unpredictable nature of physics. I was academically strong in physics but i opted for geography as one can predict the pattern of paper of geography. But in physics, you cannot guess whether the paper will be halwa or tough. Moreover, i also heard from engineers who opted for physics that marking of physics is not like that which is done in F.Sc and Engg. Here if u have answered the question 100% u will not fetch 100% marks. Thats what people say about physics.

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Whatever mind can conceive,it can achieve - W.Clement Stone