You have already completed your B.Tech. and now you want to go for M.Sc.(Physics) in correspondence mode to pursue a teaching job in colleges or universities. This appears to be a rare career path but if you have a liking for teaching Physics or it is your interest area, you can very well pursue this objective in your life.
You have already a background of Electronics and Instrumentation so you can very well choose your specialisation paper in M.Sc. as some related subject so that you can get benefit of your existing knowledge. However you are at a liberty to choose other things like Nuclear Physics or Mathematical Physics or Astrophysics or Quantum Physics or any other branch of your choice. You will have to complete a thesis work also during your M.Sc. course.
Once you select a correspondence college for your M.Sc. in Physics then you have to put a lot of efforts to get good scoring so that after your post graduation and thereafter qualifying in NET national level exam you get an edge over other NET qualified candidates as there will be many such persons eager to apply for lectureship post which at the present juncture a coveted career option.
Following are some good institutes from where you can pursue your M.Sc.(Physics) in correspondence mode -
1. Madras University's Institute of Distance Education, Chennai, Tamilnadu.
2. Alagappa University, Tamilnadu.
3. Directorate of Distance Learning, Annamalai University, Tamilnadu.
4. Kuvempu University, Karnataka.
5. Birla Institute of Technology & Science- Pilani, Rajasthan.
6. Madurai Kamaraj University, Tamilnadu.
7. Bharathiar University, Coimbatore, Tamilnadu.
Knowledge is power.