Cambridge IGCSE Physics 0625 - 3.4 Sound - Medium Required
Cambridge IGCSE Physics 0625
3.4 Sound - Medium Required
Sound is a mechanical wave, which means it requires a medium (like air, water, or solids) to travel. Unlike electromagnetic waves (like light), sound cannot travel through a vacuum.
What is a Medium?
A medium is the substance through which a wave can propagate. It can be solid, liquid, or gas.
Why is a Medium Necessary?
Sound waves are created by vibrations. These vibrations need something to bump into and pass along. In a medium, the vibrations cause particles to move, and these moving particles transfer the energy of the vibration to other particles, effectively propagating the sound wave.
How Sound Travels Through Different Mediums
Sound travels differently through solids, liquids, and gases:
Solids: Sound travels fastest through solids because the particles are closely packed together, allowing for efficient energy transfer.
Liquids: Sound travels slower than in solids but faster than in gases.
Gases: Sound travels slowest through gases because the particles are widely spaced, resulting in less efficient energy transfer.
Evidence that Sound Requires a Medium
Vacuum Experiments: Experiments have been conducted in vacuum chambers (where air has been removed) to demonstrate that sound cannot travel in the absence of a medium. When a sound source is activated in a vacuum, no sound is heard.
Astronomy: The vast majority of space is a vacuum. Therefore, sound cannot travel through space. This is why astronauts cannot hear sounds made on other planets.
Table Summarizing Sound Speed in Different Mediums
Medium
Approximate Speed of Sound (m/s)
Solid (e.g., Steel)
5000 - 6000
Liquid (e.g., Water)
1400
Gas (e.g., Air)
343 (at 20°C)
The speed of sound depends on the properties of the medium, such as its density and elasticity. Denser and more elastic materials generally allow sound to travel faster.
Suggested diagram: A diagram showing a sound wave propagating through a solid, liquid, and gas. Label the particles and show the direction of wave propagation.