X-Ray Certification Radiation Physics and Protection 2 — Questions and Answers
Question 1: Which type of radiation has the greatest penetrating power?
- Alpha particles
- Beta particles
- Gamma rays (Correct answer)
- Neutrons
Correct answer: Gamma rays
Gamma rays have the greatest penetrating power of common radiation types and can pass through dense materials.
Question 2: What is the half-value layer (HVL) of a material?
- The thickness that stops all radiation
- The thickness that reduces radiation intensity by half (Correct answer)
- The depth at which radiation becomes safe
- The layer where scatter radiation originates
Correct answer: The thickness that reduces radiation intensity by half
HVL is the thickness of a specified material that reduces radiation intensity to 50% of its original value.
Question 3: In the photoelectric effect, what happens to the incident X-ray photon?
- It is scattered at a lower energy
- It is completely absorbed by an inner-shell electron (Correct answer)
- It passes through the atom unchanged
- It splits into two lower-energy photons
Correct answer: It is completely absorbed by an inner-shell electron
In the photoelectric effect, the photon is completely absorbed by an inner-shell electron, which is then ejected from the atom.
Question 4: What unit is used to measure radiation absorbed dose in SI units?
- Rem
- Roentgen
- Gray (Correct answer)
- Curie
Correct answer: Gray
The Gray (Gy) is the SI unit of absorbed dose, equal to 1 joule of energy deposited per kilogram of tissue.
Question 5: Which of the following best describes coherent (classical) scattering?
- An incident photon ejects a photoelectron from the atom
- An incident photon interacts with the whole atom and is redirected without energy loss (Correct answer)
- An incident photon transfers partial energy to a free electron
- An incident photon converts to an electron-positron pair
Correct answer: An incident photon interacts with the whole atom and is redirected without energy loss
Coherent scattering involves a low-energy photon interacting with an entire atom and being redirected without any energy loss.
Question 6: Which radiation protection principle states that exposure should be kept as low as reasonably achievable?
- ALARA (Correct answer)
- NCRP
- BERT
- HVL
Correct answer: ALARA
ALARA (As Low As Reasonably Achievable) is the guiding principle requiring radiation workers to minimize unnecessary exposure.
Question 7: What is the primary source of occupational radiation exposure for radiologic technologists?
- Primary beam leakage
- Scatter radiation from the patient (Correct answer)
- Natural background radiation
- Radioactive contrast agents
Correct answer: Scatter radiation from the patient
Scatter radiation from the patient represents the primary source of occupational exposure for radiographers during fluoroscopy and radiography.
X-Ray Certification Radiation Physics and Protection 2
Which type of radiation has the greatest penetrating power?