Science and medicine have long been close partners. This is particularly true in radiology where the availability of imaging techniques is central to diagnosis. However, science is far more than just providing a vehicle for understanding an imaging or therapeutic process. An understanding of the science underlying a process enables the right person to develop new techniques, understand imaging limitations and develop a portfolio of research. A knowledge of scientific principles is also mandated as a result of a need to understand best and safest practice. It is no surprise therefore that radiologists are obliged to study and pass physics exams. Such exams do present a considerable challenge and the authors of this work have set about creating a volume which is intended to be an educational resource and not just a pre-exam 'crammer'. Both authors have considerable experience in teaching, supporting and examining in medical science and have developed an awareness of where those sitting professional exams have traditionally struggled. This text is a distillation of that experience.