# Travelling waves

A periodic wave is a periodic disturbance that moves through a medium.

The vibration of the source is transmitted to other particles.

The particles of the rope (or spring) perform the same movement after another.

Amplitude is equal for all particles as the wave is undamped

All particles vibrate with the same frequency

Wave length :

1. smallest distance between pairs of corresponding point on the wave train
2. distance that the wave moves in 1 periodic time

Transverse waves  :    direction of the particles in periodic motion perpendicular to the direction in which the waves travel.

Example :  simple harmonic motion travels in a rope.                                                            The rope  takes the form of a sine wavelength: length of 1 sine

Longitudinal waves: direction periodic motion of the particles is the same direction in which the waves travel.

Example:  wave travels in air

There are  condensations and rarefractions.

wavelenght : distance between the centers of two successive condensations /rarefractions

There is:

v = f . λ

• v speed of the wave  in m/s
• f frequency source in Hz
• λ wavelength  in m

Δ φ = Δ x/ λ

• Δ x  distance between two points in a wave
• Δ φ  phase difference between these two points
• λ and  Δ x : the same unit