Short Answer
Q ∝ r⁴/L is the best answer.
Biophysics questions work best when you translate anatomy or instrumentation back into plain physics: pressure gradients, flow, diffusion, energy deposition, imaging contrast, and signal-to-noise.
Poiseuille: Q = πr⁴ΔP/(8ηL) — flow scales as the fourth power of radius (halving radius reduces flow 16-fold).
Why This Answer Is Correct
This is a Easy-level question in Biophysics & Medical Physics. The prompt is really testing whether you can connect the concept to its defining physical relationship instead of picking a nearby-but-wrong term.
Clinical wording can hide a simple physics core. Strip the scenario down to transport, force, energy, or measurement first.
Choices At A Glance
- A. Q ∝ r²
- B. Q ∝ r⁴/L
- C. Q ∝ 1/r
- D. Q ∝ L/r
When similar options appear on an exam, eliminate the ones that break the core law, use the wrong units, or confuse a definition with a consequence.
Study Next
Review the related formula library
study the medical physics track
Topic Snapshot
Topic: Biophysics & Medical Physics
Difficulty: Easy
Best next move: Re-state the governing law in your own words, then solve one more example from the same topic before moving on.