Dear aspirant,

First of all, you will have to choose PCM/PCMB in your class 11. After this, prepare for KVPY, which you can give in both class 11 and class 12. If you get AIR below 250 in KVPY, you have an excellent chance of getting into IISc to pursue a BS in physics. After this you can look for masters and then PhD abroad to widen your experience and expertise.

Alternatively, you can write IISER-SCB in your class 12. If you get on the top 1 percentile in class 12, you'll be eligible for INSPIRE scholarship which amounts to about 60k every year. You can do your BS-MS in physics from IISERs and look better PhD options after that.

You can also pursue BS physics in IITs if you crack JEE Advanced but I would strongly recommend aiming to get into institutes aimed to do research. For becoming a physicist you'll most likely have to a PhD. So, there is atleast 10 long years of academic work that you'll have to do after class 12. Don't worry, you'll be able to earn a decent amount of stipend while doing your PhD.

Pursue your passion for physics on your own as well. Learn the concepts that interest you, look at what research is going on in this country and abroad and keep doing physics.

Hope this helps