PADI Divemaster Certification Practice Exam

What is the primary reason for the increased speed of sound in water compared to air?

1. Higher temperature in water

2. Elasticity of water

3. Lower pressure in water

4. Availability of larger molecules

The correct answer is: Elasticity of water

The primary reason for the increased speed of sound in water compared to air is the elasticity of water. Sound travels as a wave through a medium, and its speed is primarily determined by how easily that medium can be compressed or deformed and then return to its original state. Water is a much denser medium than air, and its molecules are more closely packed together, which means that when sound waves pass through, the energy is transmitted more effectively. The elasticity of water allows it to quickly propagate sound waves, resulting in a significantly higher speed of sound compared to air. Factors such as temperature and pressure, while they can also influence sound speed, are secondary when discussing the fundamental reason for the difference between water and air. In air, the speed of sound is slower due to its lower density and elasticity. The concept of larger molecules does not directly contribute to the speed of sound, as sound speed is more about how rapidly energy can be transferred between particles rather than the size of those particles. Thus, understanding the role of elasticity provides clarity on why sound travels faster in water.