Hello Umesh!
You can definitely apply for BTech computer science with physics and mathematics as your core subjects in class 12th. The eligibility criteria for pursuing BTech computer science is passing your class 12th with physics, mathematics and english as core subjects with 50% marks ( minimum ). Chemistry is not required to studying computer science. BTech CSE is a four year undergraduate course based in practical and theoretical knowledge of computer hardware and software. Go for it. Hope this helps.
All the best!