Medical Radiation Safety Exam
Questions with Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
Domain 1 — Radiation Fundamentals
1. What is the defining characteristic of ionizing radiation?
A. It always has a positive electrical charge
B. It can remove electrons from atoms or molecules
C. It can be seen by the human eye
D. It travels only through biological tissue
Correct Answer: B. It can remove electrons from atoms or molecules
Rationale: Ionizing radiation has sufficient energy to remove electrons from atoms
or molecules, producing ions. This property distinguishes it from non-ionizing
radiation.
2. Which type of radiation consists of electromagnetic photons?
A. Alpha particles
B. Beta particles
C. Neutrons
D. Gamma rays
Correct Answer: D. Gamma rays
Rationale: Gamma rays are electromagnetic radiation consisting of photons
emitted from atomic nuclei. Alpha and beta radiation are particulate forms of
radiation.
,3. What is the SI unit of radioactive activity?
A. Becquerel
B. Gray
C. Sievert
D. Coulomb per kilogram
Correct Answer: A. Becquerel
Rationale: The becquerel (Bq) is the SI unit of activity and represents one nuclear
transformation per second.
4. What is the SI unit of absorbed radiation dose?
A. Sievert
B. Gray
C. Becquerel
D. Roentgen
Correct Answer: B. Gray
Rationale: The gray (Gy) is the SI unit of absorbed dose and corresponds to one
joule of radiation energy deposited per kilogram of matter.
5. What is the SI unit used for equivalent dose?
A. Gray
B. Becquerel
C. Sievert
D. Watt
Correct Answer: C. Sievert
Rationale: Equivalent dose is expressed in sieverts (Sv). It accounts for differences
in biological effectiveness associated with radiation type through radiation
weighting factors.
,6. A radionuclide has a half-life of 8 hours. What fraction of its original activity
remains after 24 hours?
A. 1/2
B. 1/4
C. 1/6
D. 1/8
Correct Answer: D. 1/8
Rationale: Twenty-four hours represents three 8-hour half-lives. The activity
becomes 1/2 after one half-life, 1/4 after two, and 1/8 after three.
7. Which type of radiation generally has the greatest penetrating ability in
biological tissue?
A. Alpha particles
B. Gamma rays
C. Heavy charged particles only
D. Low-energy beta particles
Correct Answer: B. Gamma rays
Rationale: Gamma rays are highly penetrating electromagnetic radiation. Alpha
particles have very limited penetration, while beta particles generally have
intermediate penetration.
8. Which radiation interaction is particularly important for scatter produced by
diagnostic x-rays?
A. Compton scattering
B. Nuclear fission
C. Positron emission
D. Alpha decay
Correct Answer: A. Compton scattering
, Rationale: Compton scattering occurs when an x-ray photon transfers part of its
energy to an electron and changes direction. Scattered photons contribute
significantly to occupational exposure during diagnostic imaging.
9. What happens during photoelectric absorption?
A. The photon changes direction without transferring energy
B. The photon transfers all its energy to an electron and disappears
C. Two photons are produced from one neutron
D. An alpha particle becomes a gamma ray
Correct Answer: B. The photon transfers all its energy to an electron and
disappears
Rationale: In photoelectric absorption, the incident photon transfers all of its
energy to a bound electron, ejecting that electron from the atom. The incident
photon no longer exists.
10. Which quantity describes the rate at which radioactive nuclei undergo
nuclear transformations?
A. Activity
B. Absorbed dose
C. Effective dose
D. Exposure time
Correct Answer: A. Activity
Rationale: Activity describes the rate of radioactive transformations occurring in a
radioactive material. It is measured in becquerels in the SI system.
Domain 2 — Radiation Protection Principles
11. Which three principles provide the basic approach to reducing external
radiation exposure?
Questions with Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
Domain 1 — Radiation Fundamentals
1. What is the defining characteristic of ionizing radiation?
A. It always has a positive electrical charge
B. It can remove electrons from atoms or molecules
C. It can be seen by the human eye
D. It travels only through biological tissue
Correct Answer: B. It can remove electrons from atoms or molecules
Rationale: Ionizing radiation has sufficient energy to remove electrons from atoms
or molecules, producing ions. This property distinguishes it from non-ionizing
radiation.
2. Which type of radiation consists of electromagnetic photons?
A. Alpha particles
B. Beta particles
C. Neutrons
D. Gamma rays
Correct Answer: D. Gamma rays
Rationale: Gamma rays are electromagnetic radiation consisting of photons
emitted from atomic nuclei. Alpha and beta radiation are particulate forms of
radiation.
,3. What is the SI unit of radioactive activity?
A. Becquerel
B. Gray
C. Sievert
D. Coulomb per kilogram
Correct Answer: A. Becquerel
Rationale: The becquerel (Bq) is the SI unit of activity and represents one nuclear
transformation per second.
4. What is the SI unit of absorbed radiation dose?
A. Sievert
B. Gray
C. Becquerel
D. Roentgen
Correct Answer: B. Gray
Rationale: The gray (Gy) is the SI unit of absorbed dose and corresponds to one
joule of radiation energy deposited per kilogram of matter.
5. What is the SI unit used for equivalent dose?
A. Gray
B. Becquerel
C. Sievert
D. Watt
Correct Answer: C. Sievert
Rationale: Equivalent dose is expressed in sieverts (Sv). It accounts for differences
in biological effectiveness associated with radiation type through radiation
weighting factors.
,6. A radionuclide has a half-life of 8 hours. What fraction of its original activity
remains after 24 hours?
A. 1/2
B. 1/4
C. 1/6
D. 1/8
Correct Answer: D. 1/8
Rationale: Twenty-four hours represents three 8-hour half-lives. The activity
becomes 1/2 after one half-life, 1/4 after two, and 1/8 after three.
7. Which type of radiation generally has the greatest penetrating ability in
biological tissue?
A. Alpha particles
B. Gamma rays
C. Heavy charged particles only
D. Low-energy beta particles
Correct Answer: B. Gamma rays
Rationale: Gamma rays are highly penetrating electromagnetic radiation. Alpha
particles have very limited penetration, while beta particles generally have
intermediate penetration.
8. Which radiation interaction is particularly important for scatter produced by
diagnostic x-rays?
A. Compton scattering
B. Nuclear fission
C. Positron emission
D. Alpha decay
Correct Answer: A. Compton scattering
, Rationale: Compton scattering occurs when an x-ray photon transfers part of its
energy to an electron and changes direction. Scattered photons contribute
significantly to occupational exposure during diagnostic imaging.
9. What happens during photoelectric absorption?
A. The photon changes direction without transferring energy
B. The photon transfers all its energy to an electron and disappears
C. Two photons are produced from one neutron
D. An alpha particle becomes a gamma ray
Correct Answer: B. The photon transfers all its energy to an electron and
disappears
Rationale: In photoelectric absorption, the incident photon transfers all of its
energy to a bound electron, ejecting that electron from the atom. The incident
photon no longer exists.
10. Which quantity describes the rate at which radioactive nuclei undergo
nuclear transformations?
A. Activity
B. Absorbed dose
C. Effective dose
D. Exposure time
Correct Answer: A. Activity
Rationale: Activity describes the rate of radioactive transformations occurring in a
radioactive material. It is measured in becquerels in the SI system.
Domain 2 — Radiation Protection Principles
11. Which three principles provide the basic approach to reducing external
radiation exposure?
