B.Sc Physics

For B.Sc physics, you should have chosen physics, chemistry, maths and any other subjects. You need to have a good score in 12th board exams. There is no particular cut off marks, they are determined by the admin only. You need to apply online or offline. For further details regarding admission refer:
http://www.loyolacollege.edu/admission/courses-offered.php
If you belong to Tamil Nadu HSC board, then the applications for B.Sc courses are closed from 25th May.
Other board students (other state) can apply 3 days after the results of their respective boards.

To get in any top college your score should be at least 85%. In Delhi University it's always above 95%. These cut offs are mainly for the general category. If you are in reserved category then some relaxation will always be there.

Hello Prashanth,
The two links below give you the list of the colleges that offer B.Sc and B.Sc (Hons) in physics:
https://www.shiksha.com/science/colleges/b-sc-physics-colleges-india

Yes, you have the option of –
Five-year integrated BS-MS dual-degree programme in Physical Science at IISERs (Bhopal, Kolkata, Mohali, Pune and Thiruvananthapuram).

For B.Sc (Hons) in Physics, Vivekananda Global University, Jaipur is best with best faculty, well equipped lab, innovation hub, work on new ideas and projects.

Hi PJ,
B.Sc in physics is a popular option and could be one of the best if you want to do higher studies and research in Physics, in your case it's going to be optics I believe. Score well in your B.Sc, you can also look for MS options abroad for better prospects.