How much air will a diver use at a pressure of 4 ata compared to 2 ata, assuming a consistent air consumption rate?

To understand why the correct answer is that a diver will use air at a pressure of 4 ata, compared to 2 ata, at a rate of 2 times more, we can consider how pressure affects gas volume and consumption underwater.

At greater depths, the pressure exerted on a diver increases. The term "ata" refers to atmospheres absolute, which includes both the atmospheric pressure at sea level and the additional pressure from the water column above the diver. At 2 ata, the total pressure on the diver is twice that of surface pressure, while at 4 ata, the total pressure is four times that of surface pressure.

According to Boyle's law, the volume of a gas is inversely proportional to the pressure exerted on it. This means that as pressure increases, the volume of air (or any gas) decreases. However, the diver’s lungs and the rate at which they inspire and exhale air do not change with depth; they still inhale and exhale a consistent volume per breath.

Therefore, while the diver is breathing in a consistent volume of gas (in terms of the volume of air they would take from a tank), the increased pressure at 4 ata means that the diver is accessing a greater amount of air