NMTCB CNMT Exam 2026/2027 | Certified Nuclear Medicine
Technologist | 300+ Practice Questions, Correct Answers &
Detailed Rationales
DOMAIN I — RADIATION PHYSICS & DETECTION
1.
Which particle is emitted during beta-minus decay?
A. Alpha particle
B. Electron
C. Positron
D. Photon
Correct Answer: B
Rationale: Beta-minus decay converts a neutron into a proton and
emits an electron and antineutrino. The atomic number increases by
one while the mass number remains unchanged.
2.
What is the primary characteristic of gamma radiation?
A. It has a positive charge
B. It consists of helium nuclei
C. It is electromagnetic radiation
D. It has a negative charge
Correct Answer: C
,Rationale: Gamma rays are high-energy electromagnetic photons
emitted from an excited nucleus. They have no mass and no electrical
charge.
3.
Which decay process decreases atomic number by two and mass
number by four?
A. Beta-minus decay
B. Positron emission
C. Electron capture
D. Alpha decay
Correct Answer: D
Rationale: An alpha particle contains two protons and two neutrons. Its
emission therefore decreases atomic number by 2 and mass number by
4.
4.
During positron emission, a proton is converted into:
A. A neutron
B. An electron
C. An alpha particle
D. A gamma photon
Correct Answer: A
,Rationale: Positron emission converts a proton into a neutron while
producing a positron and neutrino. The atomic number decreases by
one.
5.
What happens to the atomic number during electron capture?
A. It increases by two
B. It decreases by one
C. It remains unchanged
D. It decreases by two
Correct Answer: B
Rationale: In electron capture, an inner-shell electron is captured by the
nucleus, converting a proton into a neutron. The atomic number
decreases by one while mass number remains unchanged.
6.
The half-life of a radionuclide is the time required for:
A. All activity to disappear
B. The activity to decrease to 25%
C. The activity to decrease to 50%
D. The physical volume to decrease by half
Correct Answer: C
Rationale: Physical half-life is the time required for one-half of the
radioactive atoms or activity to decay.
, 7.
A radionuclide has a physical half-life of 6 hours. What fraction remains
after 18 hours?
A. 1/2
B. 1/4
C. 1/8
D. 1/16
Correct Answer: C
Rationale: Eighteen hours represents three half-lives. The remaining
activity is (1/2)³ = 1/8.
8.
Which factor does NOT affect physical radioactive decay?
A. Temperature
B. Nuclear composition
C. Half-life
D. Radioactive isotope
Correct Answer: A
Rationale: Ordinary changes in temperature, pressure, and chemical
state do not significantly affect nuclear decay rates. The decay rate is
characteristic of the radionuclide.
9.
Technologist | 300+ Practice Questions, Correct Answers &
Detailed Rationales
DOMAIN I — RADIATION PHYSICS & DETECTION
1.
Which particle is emitted during beta-minus decay?
A. Alpha particle
B. Electron
C. Positron
D. Photon
Correct Answer: B
Rationale: Beta-minus decay converts a neutron into a proton and
emits an electron and antineutrino. The atomic number increases by
one while the mass number remains unchanged.
2.
What is the primary characteristic of gamma radiation?
A. It has a positive charge
B. It consists of helium nuclei
C. It is electromagnetic radiation
D. It has a negative charge
Correct Answer: C
,Rationale: Gamma rays are high-energy electromagnetic photons
emitted from an excited nucleus. They have no mass and no electrical
charge.
3.
Which decay process decreases atomic number by two and mass
number by four?
A. Beta-minus decay
B. Positron emission
C. Electron capture
D. Alpha decay
Correct Answer: D
Rationale: An alpha particle contains two protons and two neutrons. Its
emission therefore decreases atomic number by 2 and mass number by
4.
4.
During positron emission, a proton is converted into:
A. A neutron
B. An electron
C. An alpha particle
D. A gamma photon
Correct Answer: A
,Rationale: Positron emission converts a proton into a neutron while
producing a positron and neutrino. The atomic number decreases by
one.
5.
What happens to the atomic number during electron capture?
A. It increases by two
B. It decreases by one
C. It remains unchanged
D. It decreases by two
Correct Answer: B
Rationale: In electron capture, an inner-shell electron is captured by the
nucleus, converting a proton into a neutron. The atomic number
decreases by one while mass number remains unchanged.
6.
The half-life of a radionuclide is the time required for:
A. All activity to disappear
B. The activity to decrease to 25%
C. The activity to decrease to 50%
D. The physical volume to decrease by half
Correct Answer: C
Rationale: Physical half-life is the time required for one-half of the
radioactive atoms or activity to decay.
, 7.
A radionuclide has a physical half-life of 6 hours. What fraction remains
after 18 hours?
A. 1/2
B. 1/4
C. 1/8
D. 1/16
Correct Answer: C
Rationale: Eighteen hours represents three half-lives. The remaining
activity is (1/2)³ = 1/8.
8.
Which factor does NOT affect physical radioactive decay?
A. Temperature
B. Nuclear composition
C. Half-life
D. Radioactive isotope
Correct Answer: A
Rationale: Ordinary changes in temperature, pressure, and chemical
state do not significantly affect nuclear decay rates. The decay rate is
characteristic of the radionuclide.
9.
