Final answer:
Underwater, as external pressure decreases while ascending, the air volume breathed by a diver expands according to Boyle's law. Divers must carefully adjust to pressure changes to avoid risks such as lung over-expansion. They use techniques for equalization and manage their buoyancy with air compressed in scuba tanks.
Step-by-step explanation:
An air volume breathed underwater expands in inverse proportion to the reduction in external pressure as the diver ascends to the surface. This relationship, described by Boyle's law, states that for a given mass of gas at a constant temperature, the volume of the gas varies inversely with the pressure. This means that as a diver rises and the pressure decreases, the air in their lungs and buoyancy compensator (BCD) expand. It's important to release air at a controlled rate to avoid the dangers of an uncontrolled ascent.
At greater depths, such as 33 feet below the surface, the pressure is 2 ATA, and the air breathed by divers is compressed to one-half of its volume at the surface. The pressure felt by a diver is a cumulation of the weight of water above them and the atmosphere, with water being about 775 times denser than air. This significant difference illustrates how quickly pressure can increase underwater compared to changes in altitude on land.
Divers utilize various techniques for equalization to adapt to pressure changes and maintain the safety of air-filled cavities in the body such as ears and lungs. The concept of compressibility also plays a role, as gases can be compressed and stored in scuba tanks, providing divers with the air they need underwater.