Physics and Interactions Flashcards
7 cards from real NRRPT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Physics and Interactions flashcards as text
The concept of 'buildup factor' in gamma-ray shielding accounts for:
Answer: Secondary scattered photons that add to the transmitted dose
The buildup factor (B) accounts for scattered and secondary photons that contribute to dose beyond what the uncollided (primary) beam attenuation predicts.
The energy of a photon emitted during isomeric transition (IT) equals:
Answer: The difference in energy levels between the metastable and ground state
In isomeric transition, the nucleus de-excites from a metastable state to the ground state, emitting a gamma photon equal to the energy difference between those nuclear energy levels.
What is the primary biological significance of high-LET radiation compared to low-LET radiation?
Answer: High-LET radiation is more densely ionizing and causes complex, clustered DNA damage
High-LET radiation produces dense clusters of ionization along its track, causing complex double-strand breaks and clustered DNA damage that is harder for cells to repair.
An atom undergoes electron capture. What is emitted as a direct result of the orbital electron vacancy created?
Answer: Characteristic X-rays or Auger electrons
Electron capture creates a vacancy in an inner electron shell; this vacancy is filled by outer-shell electrons, releasing characteristic X-rays or Auger electrons.
The stopping power of a material for charged particles is described by the Bethe-Bloch equation and depends primarily on:
Answer: The charge and velocity of the particle, and the electron density of the medium
The Bethe-Bloch equation shows that stopping power depends on the particle's charge (z²), its velocity (β), and the electron density (Z/A) of the absorbing medium.
In nuclear fission of U-235, the average number of prompt neutrons released per fission event is approximately:
Answer: 2.5
Each thermal fission of U-235 releases an average of approximately 2.43 prompt neutrons (often cited as ~2.5), which is essential for sustaining a chain reaction.
The half-value layer (HVL) of a photon beam is related to the linear attenuation coefficient (μ) by:
Answer: HVL = ln(2)/μ = 0.693/μ
From the exponential attenuation equation I = I₀e^(−μx), setting I/I₀ = 0.5 and solving gives HVL = ln(2)/μ ≈ 0.693/μ.