It depends on how you steer the conversation. The interviewers normally start off with getting to know you, and your motivation behind applying for the course at Christ.
Then according to your subjects, they’ll ask a few technical questions, basic concepts of what you’d have studied in 11th and 12th. Be sure to brush up on some key concepts, current developments and issues related to your subjects.
Try to be concise and clear, don’t throw in words and concepts you don’t really know. Also, be prepared to answer personality related questions, and your potential future plan, as that will tell the professors if you’re serious about the course and the field, and if the course fits into the bigger picture of your goals.
Lastly, be confident, and dress sharp.