Question

In which of the following media does sound travel the fastest? \((A)\) Vacuum (B) Air \((C)\) Water (D) Glass

Short answer

Sound travels the fastest in glass (D).

Step-by-step solution

Understand Sound Propagation

Sound is a mechanical wave that travels through the vibration of particles in a medium. The speed at which sound travels depends on the density and elasticity of the medium.

Consider Sound in a Vacuum

In a vacuum, there are no particles to transmit the vibrations, so sound cannot travel through a vacuum. Thus, option (A) is not correct.

Assess Sound Speed in Gases

In gases like air, the particles are far apart, making the speed of sound relatively slow. Although sound can travel through air, it is not the fastest medium.

Evaluate Sound Speed in Liquids

In liquids such as water, particles are closer together compared to gases, allowing sound to travel faster than in air.

Examine Sound Speed in Solids

In solids such as glass, particles are tightly packed, which facilitates faster vibration transmission. Therefore, sound travels faster in glass than in water or air.

Make a Conclusion

Out of the given options, sound travels the fastest in glass, making option (D) the correct answer.

Key concepts

Mechanical Waves

Sound is a type of mechanical wave. A mechanical wave is a disturbance that travels through a medium, transferring energy from one particle to another. Unlike electromagnetic waves, mechanical waves need a medium to travel through. This means sound cannot propagate through a vacuum.
Sound waves are created by vibrating objects. These vibrations cause the particles in the medium to oscillate back and forth. These oscillations make nearby particles vibrate, passing the energy from one molecule to the next, moving the sound forward.
Mechanical waves can be categorized into:

• Transverse Waves: The oscillation of particles is perpendicular to the wave direction (e.g., water waves).
  
• Longitudinal Waves: The oscillation occurs in the same direction as the wave (e.g., sound waves).

Sound waves are primarily longitudinal waves. This means particles vibrate parallel to the direction the wave travels.
In summary, mechanical waves like sound need a medium to propagate, and they do so by transferring energy through particle interactions.

Speed of Sound in Different Media

The speed of sound varies depending on the medium through which it travels. This is because the propagation of sound relies heavily on how easily particles in the medium can vibrate and transfer energy. Here's a closer look at different media:

• In Gases: In a gas like air, particles are far apart, which means it takes longer for them to transfer energy from one to the next. Therefore, the speed of sound in gases is relatively slow, averaging around 343 m/s in air at room temperature.
  
• In Liquids: In liquids, particles are closer together than in gases. This proximity allows for quicker energy transfer between particles. For example, the speed of sound in water is about 1482 m/s, which is significantly faster than in air.
  
• In Solids: In solids, particles are packed tightly together. This tight packing allows energy to transfer very quickly from one particle to another. Thus, sound travels fastest in solids. For example, the speed of sound in glass can be around 5000 m/s or more.

Therefore, out of the given options, sound travels the fastest in glass due to the efficient energy transfer between its densely packed particles.

Density and Elasticity of Media

Two critical factors affecting the speed of sound are the density and elasticity of the medium.

• Density: Density refers to how much mass is in a given volume. In general, a denser medium allows sound waves to travel faster because particles are closer together, facilitating easier energy transfer. However, extremely high density can also impede movement if the medium becomes too resistant to the particles' movement.
  
• Elasticity: Elasticity is the ability of a material to return to its original shape after being deformed. Higher elasticity means that a medium can transmit sound waves more effectively by quickly restoring particle positions after the wave has passed. Materials like glass have high elasticity, which helps sound waves travel faster through them.
  For sound to travel quickly, a medium must balance both high density and high elasticity efficiently. Solids like glass are excellent conductors of sound due to their optimal combination of these properties.