Hello Keshav,
In B.Sc. Maths(Hons.) not the single subject is taught there you will learn three subjects in detail that are Physics, Chemistry and Mathematics.
In this course you will learn application of all the formulas you learned upto intermediate. Some colleges also offers some additional subjects so yoi can go for that also.
It is upto you which subjects do you take additionally.
I hope this answer helps you. For further doubts feel free to ask in comment section.
Good Luck!!
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