Book excerpt: Significant numbers of physicists began working in association with hospitals following the discovery of X-Rays and radioactivity in the late 1890s. This book introduces the reader to medical radiation physics using the developments from the early days as a means of explaining the underlying science. The first chapter provides basic information on x-rays and radioactivity. This is followed by their diagnostic and therapeutic applications. Recent developments involving non-ionising ultraviolet, visible and infrared radiations, and the use of lasers are covered in the following chapters. The last part explains the use of ultrasound and magnetic fields./a