A sound wave is used instead of an electromagnetic wave for measuring the depth at sea because sound waves travel much more efficiently through water than electromagnetic waves.
When it comes to propagating through water, sound waves have distinct advantages over electromagnetic waves. Here are a few reasons why sound waves are preferred for measuring depth at sea:
Water is a better medium for sound: Sound waves can travel through water more effectively than electromagnetic waves. Water is denser and more elastic compared to air or vacuum, which allows sound waves to propagate with less loss of energy. Electromagnetic waves, on the other hand, tend to be attenuated and scattered more easily in water, making them less suitable for long-range underwater communication or sensing.
Low absorption and long range: Sound waves experience relatively low absorption in water, which means they can travel long distances without significant loss of energy. In contrast, electromagnetic waves, especially higher-frequency waves like visible light or radio waves, can be absorbed and scattered by water molecules, reducing their range and effectiveness for underwater communication or sensing.
Reflection and echo detection: Sound waves can readily reflect off surfaces such as the ocean floor, providing valuable information about the depth of the sea. By measuring the time it takes for sound waves to travel to the seafloor and back, depth-sensing techniques like sonar can accurately determine the water depth. Electromagnetic waves, while capable of reflection, may not provide as clear and precise information about underwater structures and depths due to their interaction with the water.
Compatibility with underwater devices: Many underwater instruments, such as sonar systems and underwater acoustic sensors, are specifically designed to transmit and receive sound waves. Using sound waves for depth measurement allows for compatibility with these devices, making it easier to implement and integrate the necessary technology for underwater exploration and navigation.
Considering these factors, sound waves are the preferred choice for measuring depth at sea due to their efficient transmission in water, long range, ability to reflect off surfaces, and compatibility with underwater sensing and communication technologies.