PADI Divemaster Certification Practice Exam

Why does sound travel faster in water compared to air?

1. Water is less dense than air

2. Sound is a pressure wave that moves more efficiently through water

3. Air has a higher elasticity than water

4. Water absorbs sound energy better than air does

The correct answer is: Sound is a pressure wave that moves more efficiently through water

Sound travels faster in water compared to air primarily because sound is a pressure wave that moves more efficiently through a denser medium. In a fluid like water, molecules are closer together than in air, allowing sound waves to transmit their energy more readily from one molecule to another. The rigidity and compressibility of water also enhance this transmission efficiency. When sound waves travel, they rely on the interaction between particles to propagate. Since water molecules are packed more closely together than air molecules, the sound waves require less time to travel from one particle to another, thus resulting in faster sound movement. This efficiency is not just about density but also involves how quickly the energy of the sound wave is passed along, making water an ideal medium for sound transmission. The other options do not accurately explain the phenomenon. For instance, while water is indeed denser than air, this does not negate the speed of sound traveling through it. The statement regarding air's higher elasticity compared to water doesn't directly relate to the faster sound speed in water, and the absorption of sound energy in water compared to air does not explain why sound travels faster but refers instead to how sound diminishes over distance in different mediums.