X-RAY SUPERVISOR AND OPERATOR
CERTIFICATION EXAMINATION
CALIFORNIA RADIOGRAPHY SUPERVISOR AND
OPERATOR PERMIT
2026–2027 TESTING CYCLE
SECTION 1: RADIATION PHYSICS AND X-RAY PRODUCTION (Questions 1–20)
Question 1: X-rays were discovered by Wilhelm Roentgen in what year?
Answer: 1895.
Rationale: Wilhelm Conrad Roentgen discovered X-rays on November 8, 1895, while
experimenting with cathode rays. He observed that a fluorescent screen glowed even when
shielded and called the mysterious new rays "X-rays." This discovery earned him the first Nobel
Prize in Physics in 1901.
Question 2: Which process is primarily responsible for the production of X-rays in a diagnostic
X-ray tube?
Answer: Bremsstrahlung radiation.
Rationale: Bremsstrahlung ("braking") radiation is the primary process by which X-rays are
produced. It occurs when high-speed electrons from the cathode are decelerated by the strong
,electric fields of the tungsten target nuclei, producing a broad spectrum of X-ray energies. This
interaction causes the X-ray beam to be polyenergetic.
Question 3: The X-ray tube consists of a negative _______ and a positive _______.
Answer: Cathode; anode.
Rationale: The X-ray tube consists of a negative cathode (which contains the filament) and a
positive anode (which serves as the target). The anode includes the positive electrode and the
target. Electrons are emitted from the cathode and accelerated toward the anode, where they
collide to produce X-rays.
Question 4: Which electron interaction with the anode causes the X-ray beam to be
polyenergetic?
Answer: Bremsstrahlung.
Rationale: Bremsstrahlung radiation produces a continuous spectrum of X-ray energies, making
the beam polyenergetic. Characteristic radiation produces discrete energies but represents a
smaller portion of the X-ray beam.
Question 5: The process by which electrons are released from a heated tungsten filament is
termed:
,Answer: Thermionic emission.
Rationale: Thermionic emission is the process by which electrons are released from a heated
tungsten filament. The filament in the cathode is heated to approximately 2,200°C, causing
electrons to "boil off" and form an electron cloud (space charge) around the filament.
Question 6: Which means of X-ray production involves projectile electrons knocking out inner-
shell electrons of tungsten?
Answer: Characteristic radiation.
Rationale: Characteristic radiation occurs when projectile electrons knock out inner-shell
electrons of tungsten atoms. When an outer-shell electron fills the vacancy, a photon with a
characteristic energy specific to tungsten is emitted. This is the secondary mechanism of X-ray
production.
Question 7: Approximately what percentage of the energy deposited in the target by electrons is
converted to heat?
Answer: 99%.
Rationale: Approximately 99% of the kinetic energy of electrons striking the anode is converted
to heat. Only about 1% is converted to X-rays. This is why X-ray tubes must have efficient
cooling systems, including rotating anodes and oil immersion.
, Question 8: The three interactions electrons have with atoms at the surface of the anode are:
Answer: Heating, Bremsstrahlung, and characteristic.
Rationale: The three interactions electrons have with atoms at the surface of the anode are
heating (most common), Bremsstrahlung (X-ray production), and characteristic (X-ray
production). Understanding these interactions is fundamental to radiologic physics.
Question 9: The five interactions that X-ray photons have with matter are:
Answer: Coherent scattering, photoelectric effect, Compton scattering, pair production, and
photodisintegration.
Rationale: The five interactions that X-ray photons have with matter are coherent scattering,
photoelectric effect, Compton scattering, pair production, and photodisintegration. In the
diagnostic energy range, the photoelectric effect and Compton scattering are the most important
interactions.
Question 10: The photoelectric effect is more likely to occur with:
Answer: Low-energy photons and high-atomic-number materials.
CERTIFICATION EXAMINATION
CALIFORNIA RADIOGRAPHY SUPERVISOR AND
OPERATOR PERMIT
2026–2027 TESTING CYCLE
SECTION 1: RADIATION PHYSICS AND X-RAY PRODUCTION (Questions 1–20)
Question 1: X-rays were discovered by Wilhelm Roentgen in what year?
Answer: 1895.
Rationale: Wilhelm Conrad Roentgen discovered X-rays on November 8, 1895, while
experimenting with cathode rays. He observed that a fluorescent screen glowed even when
shielded and called the mysterious new rays "X-rays." This discovery earned him the first Nobel
Prize in Physics in 1901.
Question 2: Which process is primarily responsible for the production of X-rays in a diagnostic
X-ray tube?
Answer: Bremsstrahlung radiation.
Rationale: Bremsstrahlung ("braking") radiation is the primary process by which X-rays are
produced. It occurs when high-speed electrons from the cathode are decelerated by the strong
,electric fields of the tungsten target nuclei, producing a broad spectrum of X-ray energies. This
interaction causes the X-ray beam to be polyenergetic.
Question 3: The X-ray tube consists of a negative _______ and a positive _______.
Answer: Cathode; anode.
Rationale: The X-ray tube consists of a negative cathode (which contains the filament) and a
positive anode (which serves as the target). The anode includes the positive electrode and the
target. Electrons are emitted from the cathode and accelerated toward the anode, where they
collide to produce X-rays.
Question 4: Which electron interaction with the anode causes the X-ray beam to be
polyenergetic?
Answer: Bremsstrahlung.
Rationale: Bremsstrahlung radiation produces a continuous spectrum of X-ray energies, making
the beam polyenergetic. Characteristic radiation produces discrete energies but represents a
smaller portion of the X-ray beam.
Question 5: The process by which electrons are released from a heated tungsten filament is
termed:
,Answer: Thermionic emission.
Rationale: Thermionic emission is the process by which electrons are released from a heated
tungsten filament. The filament in the cathode is heated to approximately 2,200°C, causing
electrons to "boil off" and form an electron cloud (space charge) around the filament.
Question 6: Which means of X-ray production involves projectile electrons knocking out inner-
shell electrons of tungsten?
Answer: Characteristic radiation.
Rationale: Characteristic radiation occurs when projectile electrons knock out inner-shell
electrons of tungsten atoms. When an outer-shell electron fills the vacancy, a photon with a
characteristic energy specific to tungsten is emitted. This is the secondary mechanism of X-ray
production.
Question 7: Approximately what percentage of the energy deposited in the target by electrons is
converted to heat?
Answer: 99%.
Rationale: Approximately 99% of the kinetic energy of electrons striking the anode is converted
to heat. Only about 1% is converted to X-rays. This is why X-ray tubes must have efficient
cooling systems, including rotating anodes and oil immersion.
, Question 8: The three interactions electrons have with atoms at the surface of the anode are:
Answer: Heating, Bremsstrahlung, and characteristic.
Rationale: The three interactions electrons have with atoms at the surface of the anode are
heating (most common), Bremsstrahlung (X-ray production), and characteristic (X-ray
production). Understanding these interactions is fundamental to radiologic physics.
Question 9: The five interactions that X-ray photons have with matter are:
Answer: Coherent scattering, photoelectric effect, Compton scattering, pair production, and
photodisintegration.
Rationale: The five interactions that X-ray photons have with matter are coherent scattering,
photoelectric effect, Compton scattering, pair production, and photodisintegration. In the
diagnostic energy range, the photoelectric effect and Compton scattering are the most important
interactions.
Question 10: The photoelectric effect is more likely to occur with:
Answer: Low-energy photons and high-atomic-number materials.
