Ken Holmes is now retired but was the programme leader for the BSc (Hons) Diagnostic Imaging at the University of Cumbria (formerly St Martins College). He is one of the co-authors of Clark's Pocket Handbook for Radiographers and believes the time is right to develop a pocket physics book to use alongside the technique one. Ken started education as a clinical tutor and has worked at several higher education institutes in the UK and has taught physics and imaging principles for 30 years. Marcus Elkington is a senior lecturer in Diagnostic Imaging at Sheffield Hallam University. He has a great interest in imaging and physics related to diagnostic radiography and has been helping students understand physics for many years. Marcus feels there is a place for a pocket physics book produced in a student-friendly format that is aimed specifically at the core topic areas surrounding general radiographic imaging. Phil Harris was head of school at Medical Imaging Science at the University of Cumbria for many years and has always taken the greatest pleasure in passing on a basic understanding of radiation science to radiography students, many of whom enter into this subject with some considerable trepidation. This book has been written especially with these students in mind.