Radiography Exam Radiation Physics & Principles 1 — Questions and Answers
Question 1: Which type of radiation interaction with matter results in the complete absorption of an x-ray photon by an inner-shell electron, ejecting it from the atom?
- Compton scatter
- Photoelectric effect (Correct answer)
- Pair production
- Coherent scatter
Correct answer: Photoelectric effect
The photoelectric effect occurs when an x-ray photon is completely absorbed by an inner-shell electron, which is then ejected from the atom.
Question 2: What is the unit of absorbed radiation dose in the SI system?
- Rem
- Roentgen
- Gray (Correct answer)
- Sievert
Correct answer: Gray
The Gray (Gy) is the SI unit of absorbed dose, equal to 1 joule of energy deposited per kilogram of tissue.
Question 3: Which property of x-rays allows them to penetrate matter?
- High atomic number
- Short wavelength and high frequency (Correct answer)
- Long wavelength and low frequency
- Positive charge
Correct answer: Short wavelength and high frequency
X-rays have short wavelengths and high frequencies, giving them enough energy to penetrate matter.
Question 4: The quality of an x-ray beam is primarily controlled by which exposure factor?
- mA
- Exposure time
- kVp (Correct answer)
- SID
Correct answer: kVp
kVp (kilovoltage peak) controls the energy (quality/penetrating power) of the x-ray beam.
Question 5: Which phenomenon describes the decrease in x-ray intensity as the beam travels farther from the source?
- Attenuation
- Inverse square law (Correct answer)
- Filtration effect
- Beam divergence
Correct answer: Inverse square law
The inverse square law states that x-ray intensity is inversely proportional to the square of the distance from the source.
Question 6: Which shell electron is most likely involved in the photoelectric interaction that produces characteristic radiation?
- Outer shell (valence) electron
- M-shell electron
- K-shell (innermost) electron (Correct answer)
- Free electron
Correct answer: K-shell (innermost) electron
Characteristic radiation is produced when a K-shell electron is ejected and an outer-shell electron fills the vacancy, releasing a photon.
Radiography Exam Radiation Physics & Principles 1
Which type of radiation interaction with matter results in the complete absorption of an x-ray photon by an inner-shell electron, ejecting it from the atom?