As you have asked about the IUCAA (Inter-University Centre for Astronomy and Astrophysics) - NCRA ADMISSION TEST (INAT) for admission to PhD programme, I am giving you information about it, check below for the details

It is for a Research Scholarship towards a Ph. D. in Astronomy and Astrophysics, and Physics

Eligibility:

M.Sc., Integrated M.Sc. or B.E./B.Tech./M.E./M.Tech degrees with 55% of marks
Final-year B.Sc., 1st year M.Sc., 4th year Integrated M.Sc. and 2nd/ 3rd year B.E/ B.Tech students may also apply to be PRE-SELECTED for a research scholarship towards a Ph.D. at IUCAA for Physics, or Astronomy and Astrophysics.

Selection Procedure:

Based on the applications and referee assessments, a subset of the candidates are short-listed and invited to take the written test.
Candidates with 55% or more marks in the qualifying examination can also walk-in for the written test by producing valid photo identification and a copy of their most recent marksheet.
The final selection to the research scholarship is based on the results of the written test and two interviews.

Nature of the Written Test:

The test is of TWO hours duration.
The question paper has two parts, A and B.
Part A contains twenty objective-type questions on basic Mathematics, Physics and Electronics.
Part B contains another twenty objective-type questions from advanced Physics, Mathematics and Electronics/Engineering.