Undulatory phenomena

2.4 Conclusions about the nature of waves

An undulatory movement consists in the propagation of a vibration through a medium.

If the vibration is perpendicular to the propagation, the undulatory movement is transverse. This is the case of light, for example.

If the vibration has the same direction as the propagation, the undulatory movement is longitudinal. This is the case of sound. There can be undulatory movements which are both transverse and longitudinal, like the waves on the sea.

Important magnitudes in all undulatory movements:

Period	The time taken by a wave to pass through a point. It is represented by T
Frequency	The number of waves which pass through a point each second. Its value is the inverse of the period: f=1/T
Amplitude	The maximum elongation of the vibration which is propagated.
Wavelength	The distance between two points of equal phase. It is represented by L
Velocity of propagation	The velocity at which the crests of the waves move. The relation is expressed as: v =L/T or also v=L·f

	Transverse waves
	Longitudinal waves
	The waves of the sea
	Conclusions