Ans: D (Microwave) Ref Robbins 9th/428;Review of Radiology by Sumer Sethi 6th/166; L & B 26th/172]Injury Produced by Ionizing Radiation Robbins 9th/428Radiation is energy that travels in the form of waves or high-speed particles. Radiation has a wide range of energies that span the electromagnetic spectrum; it can be divided into nonionizing and ionizing radiation. The energy of nonionizing radiation such as UV and infrared light, microwave, and sound waves, can move atoms in a molecule or cause them to vibrate, but is not sufficient to displace bound electrons from atoms.By contrast, ionizing radiation has sufficient energy to remove tightly bound electrons. Collision of electrons with other molecules releases electrons in a reaction cascade, referred to as ionization. The main sources of ionizing radiation are x-rays and gamma rays (electromagnetic waves of very high frequencies), high-energy neutrons, alpha particles (composed of two protons and two neutrons), and beta particles, which are essentially electrons.At equi%ralent amounts of energy, alpha particles induce heavy damage in a restricted area, whereas x-rays and gamma rays dissipate energy over a longer, deeper course, and produce considerably less damage per unit of tissue. About 50% of the total dose of ionizing radiation received by the U.S. population is human-made, mostly originating from medical devices and radioisotopes. In fact, the exposure of patients to ionizing radiation during radiologic imaging tests roughly doubled between the early 1980s and 2006, mainly because of much more widespread use of CT scans.Ionizing radiation is a double-edged sword. It is indispensable in medical practice, being used in the treatment of cancer, in diagnostic imaging, and in therapeutic or diagnostic radioisotopes, but it also produces adverse short- and longterm effects such as fibrosis, mutagenesis, carcinogenesis. and teratogenesis.