Ask & Answer: India's Largest Education Community

You should be able to decide by yourself if you feel it is correct to pursue a course in MSA after completing your BDS. They are two very different fields with different scope. If you do not want to pursue dentistry and switch your line from BDS to MSA, it is entirely your choice.
The MAS educational experience seeks to develop critical administrative competencies in a supportive learning environment in conjunction with specific and clear feedback.
The basic eligibility criterion for MSA is Graduation from a 4 year, regionally accredited undergraduate program or equivalent.
The other prerequisite are maintained a cumulative grade point average of 3.0 (B) in their undergraduate studies, two letters of recommendation, Personal statement of purpose, English Proficiency test.

Aeronautical engineering is niche branch of engineering with good job prospects. B.Tech aeronautical engineering prepares students in designing and building aircraft and spacecraft. Aeronautical engineers handle design, manufacturing and maintenance of aircraft, helicopters & UAV. There are lots of good career opportunities on completion of Aeronautical engineering. You can join DRDO/ ISRO/ Aviation manufacturing or its ancillary units/ Airlines/ Air Force/ Educational Institutes/ R&D Units / IT etc.
You have following options to become Aeronautical Engineer:
(a) B.Tech in aeronautical engineering after +2 stage in PCM. You may refer to the following link for list of engineering colleges offering aeronautical engineering: https://www.shiksha.com/top-aeronautical-engineering-colleges-in-india-rankingpage-49-2-0-0-0
(b) Aeronautical Engineering is an interdisciplinary degree. You can do M.Tech in Aeronautical Engineering after B.Tech in Mechanical or Electronics & other branches.
(c) You can join Aeronautical Society of India(AeSI). The AeSI is a professional body, devoted to the advancement of aeronautical sciences and engineering in India. The AeSI conducts Associate Membership Examination twice a year. In which applicant has to clear minimum 10 level of Section-A and 10 level of Section- B with training, Internship & projects of this examination which are recognised by the Ministry of Education, at par with a Bachelors Degree(B.Tech) in Aerospace Engineering of University from India.
You may refer to the following link for a list of top Aeronautical/ Aerospace Engineering colleges in India: https://www.shiksha.com/b-tech/ranking/top-aeronautical-engineering-colleges-in-india/49-2-0-0-0. You are advised to appear for JEE and private engineering colleges entrance examinations to seek admission in B.Tech aeronautical/ aerospace engineering.

Mathematics has got a great importance in the industrial and economic development of a country. M.Sc in Mathematics is the postgraduate course in Mathematics which enables the candidates to use their mathematical knowledge in different areas. This course has got great scope and there are ample opportunities available for the M.Sc graduates.
Graduates in M.Sc Physics can find different technical jobs in public and private sector. There are many opportunities available for M.Sc Physics graduates in technical field. They can work as Observations Scientist, Assistant Scientist, Quality Control Manager, Laboratory Technician, School Science Technician or Research Analyst in any government or private organization. Apart from technical field, they can also go for teaching in government or private institutions.
Each of these two courses are very different from each other, although they are part of the same tree (M.Sc), and have equivalent scope in the world of science.