Is sound made of particles like light

Aha : Why is light faster than sound?

First we see the lightning bolt. It reaches us in a split second. The simultaneous pressure fluctuations in the air spread less quickly than thunder. The sound waves groan and pant after the much faster light waves. With a difference of three seconds, the thunderstorm is about a kilometer away, in other words: in the air, sound waves travel about 330 meters per second.

A lightning bolt or a swinging tuning fork brings air molecules out of their resting position. They then, in turn, begin to vibrate around an equilibrium position, similar to the way water molecules move up and down on the surface of a lake when you throw a stone into it. In both cases, the disturbance travels in waves from the source.

Sound waves travel even faster in concrete or iron than in air. In contrast to air molecules, the matter particles in solids are strongly bound to one another. After a disturbance, they return to their original position more quickly, the sound wave moves quickly. Concrete walls can therefore carry the construction noise to remote parts of the house.

Sound always needs a medium in order to reproduce. A tuning fork can also be struck in a vacuum chamber. But in it it remains completely inaudible, because there is no matter that transmits the vibrations.

It's different with light. Waves of light, such as those emitted from a source like the sun, can move through empty space. “The presence of matter influences the propagation of light, but it is not a prerequisite for a light wave to form,” says physicist Heinrich Kuttruff, emeritus from the Institute for Technical Acoustics at RWTH Aachen University.

“The speed of sound is so much lower than that of light because particles of matter have to be moved with sound,” explains Kuttruff. And these particles oppose any change in their state of motion with their inertia. Once they are in motion, the medium, whether air or concrete, strives due to its elasticity to return as soon as possible to a state of equilibrium in which the pressure is the same everywhere. As if nothing happened.

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