PADI PADI Physics & Physiology of Diving 1 — Questions and Answers
Question 1: Which gas law explains why a full scuba tank will show a lower pressure reading on a cold day compared to a warm day?
- Charles's Law (Correct answer)
- Boyle's Law
- Dalton's Law
- Henry's Law
Correct answer: Charles's Law
Charles's Law states that gas volume (or pressure in a rigid container) is directly proportional to temperature, so colder temperatures reduce pressure in a tank.
Question 2: According to Boyle's Law, what happens to the volume of an air space as a diver descends to greater depth?
- It decreases proportionally as pressure increases (Correct answer)
- It stays the same
- It increases with depth
- It doubles every 33 feet
Correct answer: It decreases proportionally as pressure increases
Boyle's Law states that at constant temperature, the volume of a gas is inversely proportional to the pressure applied, so air spaces compress as depth increases.
Question 3: What is 'nitrogen narcosis' and at what approximate depth does it typically begin to affect recreational divers?
- An intoxicating effect of nitrogen under pressure, often noticeable around 100 feet (30 m) (Correct answer)
- Nitrogen bubbles forming in the blood, occurring below 60 feet
- A toxic reaction to oxygen at depths below 40 feet
- Nitrogen depletion causing fatigue at any depth
Correct answer: An intoxicating effect of nitrogen under pressure, often noticeable around 100 feet (30 m)
Nitrogen narcosis is an altered state caused by the narcotic effect of nitrogen under pressure, commonly felt around 100 feet and increasing with depth.
Question 4: What physiological condition results from ascending too quickly and allowing dissolved nitrogen to form bubbles in body tissues?
- Decompression Sickness (DCS) (Correct answer)
- Oxygen Toxicity
- Hypercapnia
- Squeeze
Correct answer: Decompression Sickness (DCS)
Decompression Sickness (DCS) occurs when rapid ascent causes dissolved nitrogen to come out of solution and form bubbles in tissues and the bloodstream.
Question 5: What does Dalton's Law of Partial Pressures state in the context of scuba diving?
- The total pressure of a gas mixture equals the sum of the partial pressures of each component gas (Correct answer)
- Gas volume decreases as pressure increases
- Temperature and gas pressure are proportional
- Gas dissolves in liquid proportionally to its partial pressure
Correct answer: The total pressure of a gas mixture equals the sum of the partial pressures of each component gas
Dalton's Law states that each gas in a mixture exerts pressure independently, and the total pressure equals the sum of all partial pressures — critical for understanding oxygen toxicity and nitrox.
Question 6: At 2 atmospheres of pressure (33 feet/10 meters), what happens to the volume of a diver's lungs if they hold their breath and ascend to the surface?
- The volume doubles, risking lung overexpansion injury (Correct answer)
- The volume stays the same
- The volume halves
- The volume increases by 50%
Correct answer: The volume doubles, risking lung overexpansion injury
By Boyle's Law, halving the pressure from 2 ATM to 1 ATM doubles the gas volume, which can rupture lung tissue if the diver holds their breath during ascent.
PADI PADI Physics & Physiology of Diving 1
Which gas law explains why a full scuba tank will show a lower pressure reading on a cold day compared to a warm day?