Scuba Diving Physics and Physiology of Diving 3

Question 1

Why does sound travel approximately 4 times faster underwater than in air?

Accepted Answer

Water is denser and less compressible, transmitting pressure waves more efficiently

Answer

Water molecules are smaller, allowing sound waves to pass through without resistance

Answer

Sound slows down in air due to wind resistance, which is absent underwater

Answer

The increased pressure at depth compresses sound into faster waveforms

Question 2

A thermocline is best described as:

Accepted Answer

A distinct boundary layer where water temperature changes sharply with depth

Answer

A layer of water with high salinity and increased buoyancy

Answer

A current created by tidal forces near the seafloor

Answer

A zone of maximum visibility caused by filtered sunlight

Question 3

Which color of light is absorbed first and most rapidly as depth increases in the ocean?

Accepted Answer

Red

Answer

Blue

Answer

Green

Answer

Yellow

Question 4

What does the no-decompression limit (NDL) on a dive computer represent?

Accepted Answer

The maximum time a diver can stay at a given depth before requiring a decompression stop to ascend safely

Answer

The minimum surface interval needed between dives

Answer

The deepest allowable depth for a single tank dive

Answer

The maximum rate of ascent measured in feet per minute

Question 5

What physical phenomenon explains why objects underwater appear approximately 25% larger and 25% closer than they actually are?

Accepted Answer

Refraction of light at the water-mask air interface bends light rays toward the eye

Answer

The increased water pressure magnifies the cornea of the eye

Answer

Reduced light absorption at depth enhances the apparent size of objects

Answer

Water molecules act as natural lenses, focusing light on the retina

Question 6

What is the primary physiological reason cold water increases the risk of decompression sickness during ascent?

Accepted Answer

Cold reduces blood circulation, slowing nitrogen elimination from peripheral tissues

Answer

Cold causes lung contraction, reducing the volume of exhaled nitrogen

Answer

Cold increases metabolic rate, producing excess CO2 that displaces nitrogen

Answer

Cold water has higher oxygen content, accelerating nitrogen absorption

Question 7

During a dive, a diver notices their ears feel full and painful at 15 feet. This is most likely caused by:

Accepted Answer

Failure to equalize the middle ear against increasing water pressure

Answer

Nitrogen narcosis affecting the inner ear at shallow depths

Answer

CO2 buildup causing fluid retention in the Eustachian tube

Answer

Reverse block from expanding gas during a previous ascent