, NBDHE EXAM QUESTIONS AND ANSWERS
QUESTION 1
The x-ray was discovered by:
a. Heinrich Geissler
b. Wilhelm Roentgen
c. Johann Hittorf
d. William Crookes
Answer: b. Wilhelm Roentgen
Rationale: Wilhelm Roentgen discovered x-rays in 1895. Geissler and Hittorf developed
early cathode ray tubes, and Crookes advanced tube technology, but Roentgen was the first to
identify and document x-rays.
QUESTION 2
Which discovery was the precursor to the discovery of x-rays?
a. Beta particles
b. Alpha particles
c. Cathode rays
d. Radioactive materials
Answer: c. Cathode rays
Rationale: Cathode rays were studied extensively in vacuum tubes and led directly to the
discovery of x-rays. Radioactive particles (alpha, beta) were discovered later by Becquerel
and the Curies.
QUESTION 3
Which term describes two or more atoms that are joined by a chemical bond?
a. Ion
b. Ion pair
c. Molecule
d. Proton
Answer: c. Molecule
Rationale: A molecule is the smallest unit of a compound formed when two or more atoms
are bonded together. Ions and ion pairs involve electrical charges, and protons are subatomic
particles, not bonded atoms.
,QUESTION 4
Which is not a type of particulate radiation?
a. Alpha particles
b. Beta particles
c. Protons
d. Nucleons
Answer: d. Nucleons
Rationale: Particulate radiation includes alpha particles, beta particles, protons, and neutrons.
Nucleons is a general term for protons and neutrons within the nucleus, not a specific
radiation particle.
QUESTION 5
Which is the location where x-rays are produced?
a. Positive cathode
b. Positive anode
c. Negative cathode
d. Negative anode
Answer: b. Positive anode
Rationale: X-rays are produced at the tungsten target in the positive anode when high-speed
electrons from the cathode collide with it.
QUESTION 6
Which describes scatter radiation?
a. Radiation that exits the tubehead
b. Radiation that is more penetrating than primary radiation
c. Radiation that has been deflected from its path by interaction with matter
d. None of the above
Answer: c. Radiation that has been deflected from its path by interaction with matter
Rationale: Scatter radiation occurs when primary x-ray photons are deflected by matter,
reducing image quality and increasing exposure risk.
QUESTION 7
In dental imaging, the quality of the x-ray beam is controlled by:
, a. Kilovoltage
b. Milliamperage
c. Exposure time
d. Source-to-receptor distance
Answer: a. Kilovoltage
Rationale: Kilovoltage (kVp) controls the energy and penetrating power (quality) of the x-
ray beam. mA controls quantity, exposure time affects duration, and distance affects intensity
but not beam quality.
QUESTION 8
Increasing milliamperage results in an increase in:
a. Temperature of filament
b. Mean energy of beam
c. Number of x-rays produced
d. Wavelength of x-rays
Answer: c. Number of x-rays produced
Rationale: Higher milliamperage (mA) increases the number of electrons boiled off at the
cathode, thus producing more x-rays. It affects quantity, not quality (energy/wavelength) of
the beam
D. Both A & C - Answer Temperature of filament and number of x-rays produced
The overall blackness or darkness of an image is termed
a. contrast
b. density
c. overexposure
d. polychromatic - Answer Density
If the target receptor distance is doubled, the resultant beam will be
a. four times as intense
b. twice as intense
c. half as intense
d. one fourth as intense - Answer One fourth as intense
The latent period in radiation biology is the time between
a. initial injury and repair
b. subsequent doses of radiation
c. cell rest and cell mitosis
d. exposure to x-radiation and clinical symptoms - Answer Exposure to x radiation
and clinical symptoms
QUESTION 1
The x-ray was discovered by:
a. Heinrich Geissler
b. Wilhelm Roentgen
c. Johann Hittorf
d. William Crookes
Answer: b. Wilhelm Roentgen
Rationale: Wilhelm Roentgen discovered x-rays in 1895. Geissler and Hittorf developed
early cathode ray tubes, and Crookes advanced tube technology, but Roentgen was the first to
identify and document x-rays.
QUESTION 2
Which discovery was the precursor to the discovery of x-rays?
a. Beta particles
b. Alpha particles
c. Cathode rays
d. Radioactive materials
Answer: c. Cathode rays
Rationale: Cathode rays were studied extensively in vacuum tubes and led directly to the
discovery of x-rays. Radioactive particles (alpha, beta) were discovered later by Becquerel
and the Curies.
QUESTION 3
Which term describes two or more atoms that are joined by a chemical bond?
a. Ion
b. Ion pair
c. Molecule
d. Proton
Answer: c. Molecule
Rationale: A molecule is the smallest unit of a compound formed when two or more atoms
are bonded together. Ions and ion pairs involve electrical charges, and protons are subatomic
particles, not bonded atoms.
,QUESTION 4
Which is not a type of particulate radiation?
a. Alpha particles
b. Beta particles
c. Protons
d. Nucleons
Answer: d. Nucleons
Rationale: Particulate radiation includes alpha particles, beta particles, protons, and neutrons.
Nucleons is a general term for protons and neutrons within the nucleus, not a specific
radiation particle.
QUESTION 5
Which is the location where x-rays are produced?
a. Positive cathode
b. Positive anode
c. Negative cathode
d. Negative anode
Answer: b. Positive anode
Rationale: X-rays are produced at the tungsten target in the positive anode when high-speed
electrons from the cathode collide with it.
QUESTION 6
Which describes scatter radiation?
a. Radiation that exits the tubehead
b. Radiation that is more penetrating than primary radiation
c. Radiation that has been deflected from its path by interaction with matter
d. None of the above
Answer: c. Radiation that has been deflected from its path by interaction with matter
Rationale: Scatter radiation occurs when primary x-ray photons are deflected by matter,
reducing image quality and increasing exposure risk.
QUESTION 7
In dental imaging, the quality of the x-ray beam is controlled by:
, a. Kilovoltage
b. Milliamperage
c. Exposure time
d. Source-to-receptor distance
Answer: a. Kilovoltage
Rationale: Kilovoltage (kVp) controls the energy and penetrating power (quality) of the x-
ray beam. mA controls quantity, exposure time affects duration, and distance affects intensity
but not beam quality.
QUESTION 8
Increasing milliamperage results in an increase in:
a. Temperature of filament
b. Mean energy of beam
c. Number of x-rays produced
d. Wavelength of x-rays
Answer: c. Number of x-rays produced
Rationale: Higher milliamperage (mA) increases the number of electrons boiled off at the
cathode, thus producing more x-rays. It affects quantity, not quality (energy/wavelength) of
the beam
D. Both A & C - Answer Temperature of filament and number of x-rays produced
The overall blackness or darkness of an image is termed
a. contrast
b. density
c. overexposure
d. polychromatic - Answer Density
If the target receptor distance is doubled, the resultant beam will be
a. four times as intense
b. twice as intense
c. half as intense
d. one fourth as intense - Answer One fourth as intense
The latent period in radiation biology is the time between
a. initial injury and repair
b. subsequent doses of radiation
c. cell rest and cell mitosis
d. exposure to x-radiation and clinical symptoms - Answer Exposure to x radiation
and clinical symptoms
