Wave is defined as the propagation of periodic disturbances from one region to another, without the transfer of any material medium.
- Source of a wave: vibration or oscillation
- There is a transfer of energy from one point to another without the transfer of any material between the two points.
- Can be classified into two types: transverse waves and longitudinal waves
Transverse wave is a wave in which direction of vibration is perpendicular to the direction of movement of wave.
Examples are : water waves, waves on a string and electromagnetic waves (Radio waves, light waves).
Characteristics of Transverse waves:
- The particles oscillate perpendicularly (up and down) to the direction of travel.
- Peak: Highest point reached by the particle from its neutral position
- Trough: Lowest point reached by the particle from its neutral position
- The distance between adjacent particles remains constant, in the direction of the propagation of the wave.
Longitudinal wave is a wave in which the direction of vibration is parallel to the direction of travel of the wave
Examples are: sound waves and waves on a slinky spring.(which consists of regions of rarefaction and compression).
Characteristics of Longitudinal waves:
- The particles oscillate along (to-and-fro) the direction of travel.
- Compression: Section in which the particles are closest together
- Rarefaction: Section in which the particles are furthest apart
- The distance between adjacent particles varies from a maximum value (furthest apart) to a minimum value (closest together), in the direction of the propagation of the wave.
A wavefront is an imaginary line or surface that joined all adjacent points which have the same phase of vibration on the wave.
Any two points on a wave are said to be in phase when they have completed identical fractions of their periodic motion.
Note: Even though the diagram above shows the wavefronts for all the crests, wavefront does not have to be at the crests!
Video on transverse and longitudinal waves:
Sound represented on a pressure-distance graph
The air pressure is the highest at the compressions and lowest at the rarefactions of a sound wave.