2016 Med Phys I Lecture 3.1a(1) PreTest Question Title * 1. Name: Question Title * 2. Why is a small detector desired for narrow-beam geometry? Larger detectors are not necessary. Larger detectors are difficult to make. To limit the number of photons of all types it receives. To only detect photons that have not interacted with the target. Question Title * 3. For narrow beam geometry, we want all of the following except A large distance between detector and attenuator A thick attenuator A narrow beam A small detector Question Title * 4. Why is it sometimes important to use broad-beam geometry in calculations? In shielding calculations the conditions for narrow-beam geometry are not met and using narrow-beam geometry will lead to undershielding. Broad-beam geometry is required for dose calculations involving beams that are not tightly collimated. It makes calculating half-value layers easier, though it is not as realistic. Narrow-beam geometry can never be practically realized. Question Title * 5. Which statement does NOT correctly describe directly ionizing radiations? Directly ionizing radiation are all charged particles The interactions that these charged particles undergo are coulombic interactions. The predominant interaction that charged particles undergo with target material is a low-energy transfer of energy to atomic electrons. When uncharged particles undergo interactions with matter, they first transfer their energy to charged particles. Question Title * 6. Which of the following is NOT a true statement about directly ionizing radiation? Directly ionizing radiation deposits its energy via coulombic interactions along its path. The dominant interaction is a catastrophic collision in which large amounts of energy is transferred to a charged particle. Directly ionizing radiation is composed of charged particles. Directly ionizing radiation can produce types of indirectly ionizing radiation (such as Bremsstrahlung or characteristic x-rays). Question Title * 7. Are there any issues that are not clear to you at this time? Done