Pitkittäisaaltoja

Pitkittäisaaltoja, known in English as longitudinal waves, are a type of wave where the particles of the medium oscillate parallel to the direction of wave propagation. This means that the displacement of the medium's particles is in the same direction as the wave is traveling. Imagine a Slinky toy being pushed and pulled along its length. The compressions and rarefactions that move along the Slinky represent a longitudinal wave.

The most common example of a longitudinal wave is sound. When a sound source vibrates, it creates regions of compression (where the particles are squeezed together) and rarefaction (where the particles are spread apart) in the surrounding medium, typically air. These compressions and rarefactions travel outwards from the source as the sound wave. Another example can be seen in seismic P-waves, which are primary waves generated by earthquakes. These waves travel through the Earth's interior, causing the ground to compress and expand in the direction the wave is moving.

In contrast to transverse waves, where particle motion is perpendicular to wave direction (like ripples on water), longitudinal waves involve a forward and backward motion of the medium's particles. The speed of a longitudinal wave depends on the properties of the medium, specifically its elasticity and density. Denser and more elastic materials generally allow longitudinal waves to travel faster.