FCPS Part 1 Radiology: Radiation Physics and Safety — High-Yield Concepts

The one subject in FCPS Part 1 Radiology that doesn't overlap with the shared basic sciences — radiation units, protection principles, exposure factors and radiobiology — explained with practice MCQs.

Radiation Physics and Safety is the one subject in FCPS Part 1 Radiology that doesn't overlap with the basic-sciences papers every FCPS Part 1 candidate sits — Anatomy, Pathology, Physiology, Pharmacology, Biochemistry and Microbiology are shared across specialties, but Physics is unique to Radiology. Real subject-weight data from HighYield's Radiology bank puts it at 146 questions, a meaningful independent slice that candidates often under-revise simply because it doesn't feel like "real radiology." Below is a sample across its four core areas.

SI Units of Radiation

1. The SI unit of absorbed radiation dose is the:

A) Sievert
B) Becquerel
C) Gray ✅
D) Curie

2. The SI unit that accounts for the biological harm of different radiation types (equivalent dose) is the:

A) Gray
B) Sievert ✅
C) Roentgen
D) Curie

Principles of Radiation Protection

3. ALARA, the guiding principle of radiation protection, stands for:

A) As Low As Reasonably Achievable ✅
B) Absolute Limit for Approved Radiation Amounts
C) Applied Level of Acceptable Radiographic Absorption
D) Average Level of Attenuated Radiation Activity

4. The classic three-factor framework for minimizing occupational radiation exposure is:

A) Voltage, current, exposure time
B) Time, distance, shielding ✅
C) Collimation, grid, filtration
D) kVp, mAs, source-to-image distance

5. Per the inverse square law, if the distance from a radiation source is doubled, the exposure rate falls to:

A) One-half
B) One-quarter ✅
C) Double
D) It stays unchanged

Exposure Factors & Image Quality

6. Increasing kVp on an X-ray exposure primarily increases:

A) Beam penetration and reduces image contrast ✅
B) Patient dose only, with no effect on the image
C) Focal spot size
D) Grid ratio

7. mAs (milliampere-seconds) primarily controls:

A) Beam energy (penetrating power)
B) The quantity of X-ray photons produced, and therefore patient dose ✅
C) Image contrast only
D) Scatter radiation only

Radiobiology Basics

8. The Law of Bergonié and Tribondeau states that cells are most radiosensitive when they are:

A) Well-differentiated and slowly dividing
B) Undifferentiated and rapidly dividing ✅
C) Non-dividing and quiescent
D) Highly specialized, mature cells

Why This Section Is Worth Dedicated Revision Time

Because Physics doesn't appear on any other FCPS Part 1 paper, candidates can't lean on general medical-school revision for it the way they can for Anatomy or Pathology — it has to be studied specifically for Radiology. At roughly 146 questions in HighYield's bank, it's too large a slice to leave for the last week of prep.

Prepare with HighYield

HighYield's FCPS Part 1 Radiology bank covers Radiation Physics and Safety alongside Anatomy, Pathology, Physiology and every radiology subspecialty, each question explained. Try the first 20 questions free, no sign-in required, from the FCPS Part 1 Radiology question bank page.

Want a mixed-subject sampler across the whole paper first? See Most Repeated FCPS Part 1 Radiology MCQs: High-Yield Subjects.