PADI Physics and Gas Laws 5

Question 1

A diver fills a lift bag with 30 liters of air at 30 meters (4 ATA). When the bag reaches the surface, its volume will be approximately:

Accepted Answer

120 liters

Answer

Boyle's Law: V2 = (P1 × V1) / P2 = (4 × 30) / 1 = 120 liters at the surface.

Question 2

Which property of water makes it denser than air and affects a diver's buoyancy?

Accepted Answer

Water molecules are more closely packed together

Answer

Water's density (1000 kg/m³ vs ~1.2 kg/m³ for air) comes from the close packing of its molecules.

Question 3

The partial pressure of nitrogen at 40 meters (5 ATA) breathing air (79% N2) is:

Accepted Answer

3.95 ATA

Answer

ppN2 = fraction × total pressure = 0.79 × 5 = 3.95 ATA.

Question 4

Why do colors disappear at depth in the order red, orange, yellow, green, blue?

Accepted Answer

Water absorbs longer wavelengths (red end) of light first

Answer

Water absorbs red light most strongly, then progressively shorter wavelengths, causing colors to disappear in order of wavelength.

Question 5

An oxygen-enriched air (EANx) mix with 32% O2 reaches its maximum operating depth when ppO2 reaches 1.4 ATA. What is that depth?

Accepted Answer

111 feet (34 m)

Answer

Max ATA = 1.4 / 0.32 = 4.375 ATA → depth = (4.375 - 1) × 33 ≈ 111 feet (33.75 m, rounded to 34 m).

PADI - Professional Association of Diving Instructors Practice Test