Which of the following is the most penetration beam?: (A) Electron beam, (B) 8 MV photons, (C) 18 MV photons, (D) Proton beam
Answer is C. The order of penetration power is ? rays> electrons> a paicles. Here the 18MeV photon will have more energy than 8MeV photon. Ref: Essentials of Environmental Health, By Robe H. Friis, 2011, Page 191