CRA CRA Radiation Physics & Safety 1 — Questions and Answers
Question 1: Which type of ionizing radiation has the GREATEST penetrating power and requires the most shielding?
- Alpha particles
- Beta particles
- Gamma rays (Correct answer)
- Neutrons
Correct answer: Gamma rays
Gamma rays are high-energy electromagnetic radiation with very high penetrating power, requiring dense materials like lead for effective shielding.
Question 2: The ALARA principle in radiation safety stands for:
- All Levels Are Reasonably Adequate
- As Low As Reasonably Achievable (Correct answer)
- All Limits Are Regulated and Approved
- As Little As Reasonably Allowed
Correct answer: As Low As Reasonably Achievable
ALARA — As Low As Reasonably Achievable — is the guiding principle that radiation exposure should be minimized as much as practically possible.
Question 3: The annual occupational whole-body effective dose limit for radiation workers in the United States, as set by the NRC, is:
- 1 rem (10 mSv)
- 2 rem (20 mSv)
- 5 rem (50 mSv) (Correct answer)
- 10 rem (100 mSv)
Correct answer: 5 rem (50 mSv)
The NRC and NCRP set the annual occupational whole-body effective dose limit at 5 rem (50 mSv) for radiation workers.
Question 4: Which radiation monitoring device is worn by radiology staff to measure cumulative occupational radiation exposure?
- Geiger-Müller counter
- Ionization chamber survey meter
- Dosimeter badge (OSL or TLD) (Correct answer)
- Scintillation detector
Correct answer: Dosimeter badge (OSL or TLD)
Optically stimulated luminescence (OSL) and thermoluminescent dosimeters (TLD) worn as badges measure and record an individual's cumulative radiation dose.
Question 5: In radiographic imaging, the three cardinal principles of radiation protection are:
- Collimation, filtration, and shielding
- Time, distance, and shielding (Correct answer)
- Technique, positioning, and shielding
- kVp, mAs, and distance
Correct answer: Time, distance, and shielding
Time (minimize exposure time), distance (maximize distance from source), and shielding (use protective barriers) are the three cardinal principles of radiation protection.
Question 6: The inverse square law states that radiation intensity is related to distance by which relationship?
- Intensity increases proportionally as distance increases
- Intensity decreases proportionally to the square of the distance (Correct answer)
- Intensity remains constant regardless of distance
- Intensity doubles as distance doubles
Correct answer: Intensity decreases proportionally to the square of the distance
The inverse square law states that radiation intensity decreases proportionally to the square of the distance from the source (I ∝ 1/d²).
CRA CRA Radiation Physics & Safety 1
Which type of ionizing radiation has the GREATEST penetrating power and requires the most shielding?