If you want to do MSc from the IIT's then you have to qualify the IIT JAM examination Physics. The eligibility for the examination is that you should have 55% or 6 CGPA in your BSc Physics/ BSc PCM. Now the form fill up for IIT JAM 2022 will start from 30/08/2021 and you can apply for it if you are appearing in 2022 final year or if you have passed your graduation.

To know more about the IIT JAM visit the link below:

https://university.careers360.com/exams/jam

For the official website visit the link below:

https://jam.iitr.ac.in/

To know more about IIT Madras visit the link below:

https://www.careers360.com/university/indian-institute-of-technology-madras

I hope this answer helps. All the very best for your future endeavors!