M.Sc

You can get all the information about choosing astrophysics as a career. In India, you can pursue it at IISC Bangalore, Pune, Punjab university etc. Explore this:
http://www.iiap.res.in/opportunities/career

Any science graduate is eligible for M.Sc. in forensic science. You may evaluate NICFS, Delhi under GGSIPU for forensic science studies.

You can get a job as medical lab technician if you have completed your B.Sc. A Master's degree is always an added advantage. But you haven't mentioned the stream of your graduation so I cannot be confident enough if you get your Masters in microbiology because mostly microbiology and biotechnology graduates are preferred for such course. All the best.

Hi,
There are many fields waiting for you after B.Sc like: M.Sc in botany, zoology and chemistry. They all have good career opportunities. After completing this, you can join as a lecturer in any college.
Best of luck.

Below mentioned are the good branches:
1. Nuclear physics and technology.
2. Applied solid state physics.
3. Thermodynamics and statistical mechanics.
4. Electromagnetism.
5. Quantum mechanics.