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. In this article, we will learn what is a longitudinal wave and its characteristics.
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What Is Longitudinal Wave?
Longitudinal waves are waves where the displacement of the medium is in the same direction as the direction of the travelling 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.
Compression in a longitudinal wave is a region where the particles are the closest together while rarefaction in a longitudinal wave is a region where the particles are spread out.
Similar Reading: Transverse Waves
Longitudinal Wave Formula
\(\begin{array}{l}y(x,t)=y_{0}cos[\omega (t-\frac{x}{c})]\end{array} \) |
Where,
- y is the displacement of the point on the travelling sound wave
- x is the distance the point travelled 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).
The frequency (f) of the wave is given by the formula:
f=ω2π
Hope you have understood what is a longitudinal wave along with its formula. Let us now learn about sound waves and pressure waves in detail.
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.
See the video below to understand the motion of longitudinal waves and transverse waves.
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 in a longitudinal wave takes place when the particles are farthest 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
What happens when a pebble is dropped into a pond with still water?
State true or false: Mechanical waves are also known as elastic waves.
Name the condition in which sound waves can travel through the gas.
What is a mechanical wave?
A mechanical wave is a type of wave that is generated by the oscillation matter, which transmits energy through the propagating medium.
What are the two types of mechanical waves?
Longitudinal waves and transverse waves are the two types of mechanical waves.
What is meant by a longitudinal wave?
A longitudinal wave is a type of wave in which the medium’s vibration is parallel to the direction of the wave, and the medium’s displacement is in the same direction as that of the wave movement.
What are the main characteristics of a longitudinal wave?
Compression, rarefaction, wavelength, amplitude, period and frequency are the main characteristics of a longitudinal wave.
What are the familiar examples of longitudinal waves?
Tsunami waves, seismic-P waves, sound waves, and vibration in spring are some of the familiar examples of longitudinal waves.
What are the main differences between a Longitudinal wave and a transverse wave?
A longitudinal wave is a type of wave that travels in the direction of the medium, but a transverse wave is another type of wave that travels in the direction of the medium. Longitudinal waves are made of compressions and rarefactions, while transverse waves are made of crests and troughs.
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