Cambridge IGCSE Physics 0625

Topic: 3.4 Sound

Objective: Know that the speed of sound in air is approximately 330-350 m/s

This section focuses on the properties of sound waves, with a particular emphasis on the speed at which sound travels through air. Understanding the speed of sound is fundamental to comprehending phenomena like echoes and the perception of sound.

What is Sound?

Sound is a mechanical wave, which means it requires a medium (like air, water, or solids) to travel. Sound waves are longitudinal waves, meaning the particles in the medium vibrate parallel to the direction the wave is traveling.

Factors Affecting the Speed of Sound

The speed of sound depends on several factors:

• Medium: Sound travels faster in denser mediums.
• Temperature: The speed of sound increases with temperature.
• Humidity: Higher humidity slightly increases the speed of sound in air.

Speed of Sound in Air

The speed of sound in air is approximately 330 m/s at 0┬░C. This speed increases by about 0.6 m/s for every 10┬░C increase in temperature. Therefore, at room temperature (around 20┬░C), the speed of sound is approximately 340 m/s.

Calculating the Speed of Sound

The speed of a wave (v) is related to its wavelength (╬╗) and frequency (f) by the equation:

For sound waves, the wavelength is the distance between two consecutive compressions or rarefactions. The frequency is the number of compressions or rarefactions that pass a point per second.

Typical Speed of Sound in Air at Different Temperatures

Real-World Applications

Understanding the speed of sound is crucial in various applications:

• Echoes: The time it takes for sound to travel to an object and back determines when we hear an echo.
• Sonar: Sonar uses sound waves to detect objects underwater. The time delay of the returning echo is used to calculate the distance to the object.
• Medical Imaging: Ultrasound uses high-frequency sound waves to create images of internal body structures.