1. What Is the Speed of Sound?
2. Formula for Speed of Sound
The basic relation between speed, frequency, and wavelength is:
\( v = f \lambda \)
Where:
\( v \) → speed of sound
\( f \) → frequency
\( \lambda \) → wavelength
2.1. Meaning of the Formula
If the frequency of vibration increases or the wavelength increases, the speed of the wave becomes larger. But in most cases, frequency is fixed by the source, and speed mainly depends on the medium.
3. Speed of Sound in Different Media
Sound travels at different speeds depending on how close the particles are in the medium.
3.1. Speed in Solids
Particles in solids are packed closely and have strong connections. Vibrations move quickly from particle to particle, so sound travels fastest in solids.
3.1.1. Example
Sound moves faster through a metal rod than through air. Tapping one end of an iron rod can be heard at the other end almost immediately.
3.2. Speed in Liquids
Particles in liquids are fairly close but not as tightly packed as in solids. Sound travels slower than in solids but faster than in gases.
3.2.1. Example
Underwater sounds can be heard clearly because sound moves well through water.
3.3. Speed in Gases
Particles in gases are far apart. It takes longer for vibrations to pass, so sound travels slowest in gases.
3.3.1. Example
Shouting across an open field takes time to reach someone far away because sound moves relatively slowly in air.
4. Typical Speeds of Sound
The actual speed of sound varies depending on the medium. The values below show approximate speeds:
- Air: about 340 m/s
- Water: about 1500 m/s
- Iron: about 5000 m/s
5. Effect of Temperature on Speed
As temperature increases, particles in air move faster and can transfer vibrations more quickly. This increases the speed of sound.
5.1. Reason
Warm air has more energetic particles, so the disturbance passes quicker. Cold air slows down particle motion and reduces the speed of sound.
6. Effect of Humidity on Speed
Higher humidity means more water vapour in the air. Water vapour particles are lighter than dry air particles, so sound travels slightly faster in humid air.
6.1. Everyday Observation
Sound often feels clearer on humid or rainy days because the wave moves faster through moist air.