Transverse and Longitudinal Waves – Learn

Mechanical waves are classified based on how the particles propagate in the medium as energy passes through it.

In transverse waves the particles oscillate at right angles to the direction of energy transfer. Examples of transverse matter waves include a water wave, a wave in a rope, or a guitar string. In longitudinal waves the particles oscillate in the same direction as the direction of energy transfer. Examples of longitudinal matter waves include a sound wave and some earthquake waves. When longitudinal waves pass through a solid medium, then the energy transfers through high and low pressure regions within the medium. Longitudinal waves are also very difficult to draw using typical ‘dotty’ diagrams where each dot represents a particle of the medium, so we often represent them as transverse wave diagrams too. Important terms:

• Wavelength: The distance from one point on the wave to the next identical point on the wave. This is measured in centimetres or metres.
• Period: The time it takes one wave to pass a point, measured in seconds or milliseconds.
• Frequency: The number of wavelengths that pass a point each second. Frequency is measured in hertz (Hz).
• The energy carried by a wave depends on its frequency and amplitude. The higher the frequency and the larger the amplitude, the more energy the wave carries.
• Amplitude: The distance from the zero displacement position of the matter particles to a maximum displacement position (a crest or trough). It is measured in centimetres or metres.
• Zero displacement position indicates where the particles would be if no energy was being transferred through the medium.
• Crest: The position of maximum upward displacement of a particle – the ‘top of the wave’.
• Trough: The position of maximum downward displacement of a particle – the ‘bottom of the wave’.