Question

Why do scuba divers need to exhale air when they ascend to the surface of the water?

Short answer

Due to the decrease in pressure, scuba divers need to exhale air when they ascend to the surface of water. The principle behind this is Boyle's law.

Step-by-step solution

Given information

We are to find why do scuba divers need to exhale air .

Simplify

According to Boyle's Law, the pressure is inversely related to volume, which means the volume increases with the decrease in pressure.

The pressure lowers as the diver ascends. This causes the lungs' volume to expand. The diver must exhale to compensate for the volume shift brought on by the pressure change; otherwise, the expanding air will lead him to lose control of his buoyancy (The tendency to float when submerged in water/any liquid).