Dr. Ashok Ramrao Biradar, M. Sc., Ph. D. working as an Asst. Professor & Head of the Department of Physics at Shivaji Mahavidyalaya Renapur, Latur. He received his M. Sc. degree from Dr. Babasaheb Ambedkar Marathwada University, Aurangabad. He was awarded Ph. D from NIMS University Jaipur, Rajasthan. He has experience of working as a Moderator in Aurangabad board (8 Terms) & as an Assistant Moderator Latur Board (2 Terms). He has 25 years of teachings experiences at Rajshri Shahu Mahavidyalaya, Latur.          He is an author of many books on physics for Std. XII & CET published by various publishers. He was engaged in research work & participated in seminar & workshops at National & State level. He has published 4 research papers in reputed journals.          The author has put his soul into this book to make it up to date & acceptable to the students as well as the teachers of the subject.