What Is A Wave?

Show/Hide Sub-topics (General Wave Properties | O Level)

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 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:

1. The particles oscillate perpendicularly (up and down) to the direction of travel.
2. Peak: Highest point reached by the particle from its neutral position
3. Trough: Lowest point reached by the particle from its neutral position
4. The distance between adjacent particles remains constant, in the direction of the propagation of the wave.

Longitudinal waves

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:

1. The particles oscillate along (to-and-fro) the direction of travel.
2. Compression: Section in which the particles are closest together
3. Rarefaction: Section in which the particles are furthest apart
4. 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.

Wavefront

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.