MCQ Detailed View

The speed of sound in a medium depends on two main factors: the elastic properties (bulk modulus) and the density of the medium. In gases, temperature and pressure strongly affect sound speed. In liquids such as water, temperature, density, and compressibility play a major role.

At 20 °C, the speed of sound in pure water is approximately 1474 m/s. This is much faster than the speed of sound in air at the same temperature (about 343 m/s). The reason for this difference is that water is far less compressible than air. Sound travels faster when particles are closely packed and can transmit vibrations efficiently.

The relationship can be expressed by the formula:

v=Kρv = \sqrt{\frac{K}{\rho}}v=ρK

Where:

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  $v$ = speed of sound

  
  


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  $K$ = bulk modulus of the medium (measure of incompressibility)

  
  


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  $\rho$ = density of the medium

  
  

In water, although density is higher than in air, its bulk modulus is extremely large, allowing sound waves to propagate rapidly.

The speed of sound in water also varies slightly with temperature, salinity, and pressure. For instance:

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  At lower temperatures (0–5 °C), sound travels slightly slower.

  
  


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  As temperature increases, the speed increases up to a point.

  
  


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  In seawater, salinity and depth (pressure) further raise the sound speed.

  
  

This property of sound in water is widely used in sonar systems, underwater navigation, submarine communication, and marine biology research. Accurate knowledge of sound velocity in water is crucial for locating objects, mapping ocean floors, and studying marine life.

In conclusion, at 20 °C, the correct speed of sound in water is 1474 m/s. This high value compared to air highlights how the physical properties of a medium strongly influence wave propagation.