Hello Aswathi,
Congratulations!! You deserve a huge round of applause for securing high marks in +2 exam. Hope you will keep the same pace in your future studies.

For Physics based study there are two things you have to understand.

There are two streams: theoretical and experimental. Theoretician is the one who does study on phenomena with the help of mathematics. He uses computer programs to solve mathematical equations that describes the theory. He develops or propose new theory to explain phenomena. On the other hand, an experimentalist tries to prove that the theory is correct, by showing evidences using experiments and results. An experimentalist must know the theory as well as knows how to test the theory in a laboratory using sophisticated instruments. During the experiment, he may find new phenomena and may seek help from theoretician to explain it. It is purely based on your skills and fascinations whether you have to do theory or experiment.

If you are really good at mathematics you may select theoretical, else experimental study. By pursuing BSc physics and then MSc Physics you can develop both skills. Of course! you can do physics after your B Tech in some selected areas. However, B Tech trains you more in experimental side. Being said that, it does not mean that you can not do theory, certainly you can. One of the B Tech course that help you to do physics is communication engineering. You may find a potential career in quantum technologies which is considered as one among the technology for the future that involves a lot of physics. B Tech in computer science in another field that helps you to find career in theoretical physics that involves a lot of computer simulations.

However, because you are interested in physics, I would suggest you to go for traditional course like BSc physics in your local university and then MSc physics in prime institutes like IITs or central universities.

Best wishes.