Best universities for Physics undergraduate
University of Calcutta(CU) have some the best colleges in India for doing BSc Physics (Hons). And this is clear from the fact that till today CU has the 2nd largest number of students every year that clear NET/CSIR for PhD studentship in Natural Science in India. (See here CSIR-UGC Central Govt document : ). Its astonishing that even having so many Universitites in India, just only 4 University from Bengal (CU, JU, DU, KU) together has the highest share of the students within Indian that clear the CSIR-UGC PhD fellowship and start PhD. Also remember most of the faculty (in Physics and Chemistry) in most of the serious natural science research Institute (like IISc, IISER, TIFR) in India are from University of Calcutta or from other University (BU, JU, KU) from Bengal.
Being the first Physics dept created in India by S N Bose, M N Saha and chaired by many famous luminaries like S N Bose, M N Saha, C V Raman and others, it has a long history, first and only Nobel Prize in Physics in India, several prominent Royal Society fellows, continued tradition of creation and maintaining good teachers, best practical laboratories in India, largest alumni base in Physics that spread all over the world and India. But its very quite difficult to enter there as its kind of insulated from the the students from the other states. Only Bengal's students can enter there (kind of) based on Higher Secondary marks and/or entrance exam.
Also some colleges of Delhi University has very good Physics depratment. Also you will find some other universities in India that I am not aware of, can have effective good Physics department.
IISER's are just started and its mainly evolving as serious research institute but still its does not have good name in teaching, rather the common experience is pretty negative, I would say as it is till now stay away from IISER (but thats my personal opinion).
ISI, CMI, IIT, NISER, BITS all these instutute rightfully have footstep in their own specilaization (like ISI in Statistics, CMI in Math, IIT in Engg..) but not anything specially for Physics.
Rather I would say TIFR is pretty good serious place for Physics (if they provide BSc at all), IIT Kanpur has good name in Physics (specifically only for MSc). IISC so far I know dont give BSc (Physics) degree but a 4 year BS and that should be a serious good program.