Ph.D

The required minimum qualification for admission to a Ph.D. programme shall normally be a two years Masters or M.Phil Degree from any accredited Indian or Foreign University in the relevant field. She/he must have obtained 55% marks or Equivalent Grade in the master's.

As Physics and environmental studies are kind of different subjects:-
I think it is not possible ( Try asking your professors they might help )
1) M.Sc. Or M.Phil in environmental Science and other related fields. Those with M.Phil qualifications need not attend the entrance test but other postgraduates have to appear for both entrance as well as interview. It takes a minimum of 3-5 years to complete the programme.
2) candidates should have passed M.Phil. Degree and a Post-Graduate degree in a relevant discipline with a minimum of 55% marks or an equivalent grade from a University or a recognized institution of higher training.

Do you want to know about the private or government colleges?

Kurukshetra University cut off and merit lists 2021 has been released for UG and PG programmes.
Visit link: https://www.shiksha.com/university/kurukshetra-university-24587/cutoff

Hi. You can do distance Ph.D. in Math from IGNOU and Lovely Professional University.

Hi. You can do it from IGNOU. Thanks.

Hi. For more information, you can see the link given below-
https://www.shiksha.com/college/government-vishwanath-yadav-tamaskar-post-graduate-autonomous-college-durg-117051/course-ph-d-in-zoology-604901
Thanks.

Hi, here is the list of colleges-
University of Delhi
National law university, Delhi
Maharashtra National law university, Mumbai
JMI, New Delhi
Thanks.

Hi. You can do part time Ph.D. in Chemical Engineering from Lovely professional University and also you can do online from University of Dakota. Thanks.

Hi. You can do Ph.D. from Andhra University only.
For information, you can see the link given below-
https://www.shiksha.com/university/Andhra-university-Visakhapatnam-2948/courses/phd-bc
Thanks.