This Book 3 of a series of three books adequately covers the new NERDC curriculum for Senior Secondary School Physics, providing theory, laboratory work and evaluation exercises, including multiple-choice questions in each chapter. The series also covers all the topics for the Senior Secondary School Certificate Examinations in all the other West African countries, and the UTME examinations. Students are expected to study Books 1 and 2 in SS 1 and SS 2 respectively, before studying Book 3 in SS 3. By so doing, they would have covered adequately all the topics listed in the Senior Secondary School Physics curriculum. This is how the three books should be used so as to derive maximum benefit from them. The contents of each book in the series are organised in a spiral form, moving from the simple topics in Book 1 to the more complex topics in Books 2 and 3. There is no doubt that this approach aids learning.