Mechanical waves are classified as longitudinal waves and transverse waves. Some examples of longitudinal waves are sound waves, seismic P-waves, and ultrasound waves. Transverse waves examples include electromagnetic waves and ocean waves.
| Mechanical Waves
In Physics, we define wave as an oscillation about a fixed point, that is accompanied by the transfer of energy. When the transfer of energy takes place through a medium due to oscillation, the resultant wave is termed as a mechanical wave. |
In transverse waves, the displacement of the particle is perpendicular to the direction of propagation of the wave.
In a longitudinal wave, the displacement of the particle is parallel to the direction of the wave propagation.
In this article, let us familiarize ourselves with longitudinal waves and their characteristics.
What Is Longitudinal Wave?
Longitudinal waves are the waves where the displacement of the medium is in the same direction as the direction of the travel of the wave.
The distance between the centres of two consecutive regions of compression or the rarefaction is defined by wavelength, λ. When the compression and rarefaction regions of two waves coincide with each other, it is known as constructive interference and if the regions of compression and rarefaction do not coincide, it is known as destructive interference.
Similar Reading: Transverse Waves
Sound Waves
A sound wave is an example of a longitudinal wave and is produced by the vibrating motion of the particles that travel through a conductive medium. An example of sound waves in a longitudinal direction is the tuning fork.
In Sound waves, the amplitude of the wave is the difference between the maximum pressure caused by the wave and the pressure of the undisturbed air. The propagation speed of sound depends upon the type, composition of the medium, and temperature through which it propagates.
Longitudinal Wave Formula
| \(y(x,t)=y_{0}cos[\omega (t-\frac{x}{c})]\) |
Where,
- y is the displacement of the point on the traveling sound wave
- x is the distance the point traveled from the wave’s source
- t is the time elapsed
- y0 is the amplitude of the oscillations
- c is the speed of the wave
- ω is the angular frequency of the wave
Quantity x/c = time ( wave takes to travel the distance x).
Frequency (f) of the wave is given by the formula:
f=ω2π
Pressure Waves
The pressure wave is defined as the propagation of disturbance in a medium as the pressure varies.
A harmonic pressure wave oscillation will be,
| y(x,t)=y0cos(kx-ωt+φ) |
Where,
- y0 is the amplitude of displacement
- k is the wavenumber
- x is the distance along the axis of propagation
- ω is the angular frequency
- t is the time
- φ is the phase difference
Characteristics of Longitudinal Waves
Compression
In a longitudinal wave, compression is a region in which the particles of the wave are closest to each other.
Rarefaction
Rarefaction is a longitudinal wave is when the particles are furthest apart from each other.
Wavelength
The distance between two consecutive points in a longitudinal wave is known as wavelength. These consecutive points can be between two compressions or between two rarefactions.
Amplitude
Amplitude is the maximum displacement of the particle from its rest point. In a longitudinal wave, the distance from the equilibrium position in the medium to compression or rarefaction is the amplitude.
Period and Frequency
The time taken by the wave to move one wavelength is known as the period.
The frequency of the longitudinal wave is the number of wavelengths per second.
Difference Between Longitudinal And Transverse Wave
| Longitudinal Wave | Transverse Wave |
| A wave that moves in the direction of its propagation | A wave that moves in the direction perpendicular to its propagation |
| A sound wave is an example of a longitudinal wave | Water waves are an example of a transverse wave |
| It is made of refractions and compressions | It is made of troughs and crests |
| This wave can be produced in any medium such as gas, liquid or solid | This wave can be produced in solid and liquid’s surface |
Read More:Difference Between Longitudinal Waves and Transverse Waves
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Frequently Asked Questions – FAQs
The longitudinal wave formula is given by the equation _____.
List the characteristics of sound?
The characteristics of the sound are as follows:
- Loudness
- Pitch
- Quality
