Scuba Diving Physics and Physiology of Diving 1 — Questions and Answers
Question 1: How much does absolute pressure increase for every 33 feet (10 meters) of seawater depth?
- 1 ATM (14.7 psi) (Correct answer)
- 2 ATM (29.4 psi)
- 0.5 ATM (7.35 psi)
- 3 ATM (44.1 psi)
Correct answer: 1 ATM (14.7 psi)
Seawater pressure increases by 1 atmosphere (14.7 psi) for every 33 feet (10 m) of depth, so at 33 ft the absolute pressure is 2 ATM total.
Question 2: According to Boyle's Law, if a diver exhales a 4-liter bubble at 66 feet (3 ATM absolute), what volume will it be at the surface?
- 12 liters (Correct answer)
- 8 liters
- 6 liters
- 4 liters
Correct answer: 12 liters
Boyle's Law states P1V1 = P2V2; at 3 ATM, 4 L × 3 = 12 L at 1 ATM on the surface.
Question 3: Which gas law explains why a diver's lungs could rupture if they hold their breath while ascending?
- Boyle's Law (Correct answer)
- Henry's Law
- Dalton's Law
- Charles's Law
Correct answer: Boyle's Law
Boyle's Law shows that gas volume expands as pressure decreases on ascent; holding your breath traps expanding gas that can over-pressurize the lungs.
Question 4: Henry's Law, as it applies to scuba diving, describes which phenomenon?
- More gas dissolves into blood as pressure increases (Correct answer)
- Gas volume shrinks as temperature drops
- Partial pressures of gas mixtures are additive
- Buoyancy depends on displaced water weight
Correct answer: More gas dissolves into blood as pressure increases
Henry's Law states that the amount of gas dissolved in a liquid is proportional to the partial pressure of that gas, which is why nitrogen absorbs into tissues at depth.
Question 5: What is nitrogen narcosis most commonly compared to in terms of its effect on a diver?
- Alcohol intoxication (Correct answer)
- Carbon monoxide poisoning
- Severe dehydration
- Hyperventilation
Correct answer: Alcohol intoxication
Nitrogen narcosis causes impaired judgment, euphoria, and reduced motor skills at depth, effects that closely resemble alcohol intoxication.
Question 6: At approximately what partial pressure of oxygen (ppO2) does acute CNS oxygen toxicity become a significant risk?
- 1.6 ATA (Correct answer)
- 0.21 ATA
- 0.5 ATA
- 2.5 ATA
Correct answer: 1.6 ATA
A ppO2 above 1.6 ATA is the widely accepted limit where CNS oxygen toxicity risk rises sharply, which is why dive agencies set this as the recreational maximum.
Question 7: What physiological change occurs in a diver's body that directly causes decompression sickness (DCS)?
- Dissolved nitrogen forms bubbles in tissues and blood on ascent (Correct answer)
- Oxygen is consumed faster than it can be replenished
- Carbon dioxide builds up to toxic levels in the bloodstream
- Ear pressure fails to equalize, damaging inner ear tissue
Correct answer: Dissolved nitrogen forms bubbles in tissues and blood on ascent
DCS results from nitrogen that dissolved under pressure coming out of solution too quickly on ascent, forming bubbles in tissues and blood vessels.
Scuba Diving Physics and Physiology of Diving 1
How much does absolute pressure increase for every 33 feet (10 meters) of seawater depth?