Hey there, Aravinth. The best colleges providing B.sc (Physics) in TamilNadu are:

1. Loyola College

NAAC Accrediation: 3.70/4.0 Grade "A"

Process of Admission: Merit List/Selection List Published by College 

2. Stella Maris College

NAAC Accrediation: 3.68/4.00 Grade "A"

Process of Admission: Students are provisionally selected on their marks scored in Class 12th and they are called for Interview.

3. Sri Ramakrishna College of Arts and Science

NAAC Accrediation: Grade "A"

Process of Admission: On the basis of marks scored in Class 12th. 

4. Seethalakshmi Ramaswami College 

NAAC Accrediation: Grade "A"

Process of Admission: On the basis of marks scored in Class 12th. 

4. Srimad Andavan Arts and Science College

NAAC Accrediation: Grade "A"

Process of Admission: Class 12th Marks 

5. Dr. NGP Arts and Science College

NAAC Accrediation: Grade "A"

Process of Admission: Students are selected on the basis of marks scored in Class 12th. 

6. The New College

NAAC Accrediation: Grade "A"

Process of Admission: Merit List Released by College

There are more private institutions which come under Grade "B" Colleges as accrediated by NAAC. But, you must try to take admission in the above colleges. Wish you all the best.