Everything about Longitudinal Waves

Transverse and longitudinal waves come under the category of mechanical waves. The longitudinal wave examples include ultrasound waves, seismic p waves. Sound is also a longitudinal wave. On the other hand, some of the examples of transverse waves include ocean waves and electromagnetic waves. In this article, we will talk about longitudinal waves, their formulas, and their types. 

What is a longitudinal wave, and how does it work?

Longitudinal waves are those in which the medium displacement is in the same direction as the wave’s travel direction.

The wavelength is the distance between the centers of two consecutive compression or rarefaction areas. Constructive interference occurs when the compression zones of two waves coincide, whereas destructive interference occurs when the compression zone of one wave and rarefaction zone of another wave  coincide.

Definition of a longitudinal wave

In longitudinal waves, medium displacement takes place in the same direction as the direction of travel of the wave. The distance between center points of two consecutive areas of rarefaction and compression is known as wavelength, λ. 

At the time when the compression region of two different waves collide with one another, the occurrence is known as constructive interference. 

At the time when a region of rarefaction and a region of compression collide with each other, it  is termed as destructive interference. 

 Longitudinal wave formula

y(x,t)=y0 cos[ω(t-x/c)]

Here,

y is the displacement of the point on the traveling sound wave. 

x is 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) is time that wave takes to travel the distance x

The formula gives frequency (f) of the wave:

f=ω/2π

Characteristics of longitudinal waves

• Compression

In longitudinal waves, compression refers to an area in which wave’s particles are nearest to one another. 

• Rarefaction

It occurs when particles are far away from one another. 

• Wavelength

In a longitudinal wave, the distance measured between two consecutive locations is called wavelength. These consecutive locations can take place between two rarefactions and between two compressions.

• Amplitude

Amplitude is known as the highest particle’s displacement from the point of its rest. In longitudinal waves, the measured distance from the position of equilibrium in the medium to rarefaction and compression is the amplitude.

• Period and Frequency

The time that a wave takes to travel one wavelength is called the period. The longitudinal wave’s frequency refers to the number of wavelengths/second. 

Examples of longitudinal waves

Here are three examples of longitudinal waves:

• Sound waves
• Ultrasound waves
• Seismic P-waves

Sound waves 

Sound wave is the first of the longitudinal wave examples. It is defined as the disturbance pattern due to the movement of energy in the same direction as propagation of waves. Here, by source, we mean an object that starts the vibration—for example, the vocal cord of a person or a ringing telephone.  

Ultrasound waves

Sound waves that have a frequency level more than human hearing’s upper audible limit are known as ultrasound. However, the limit differs from person to person, but usually, it is around 20,000 Hz. The physical ultrasound properties resemble the standard audible sound. 

The scientific concept of ultrasound has been in active use in various fields like imaging, navigation, communication, medicine, cleaning, testing, mixing, and so on. In natural wildlife, porpoises and bats utilize the specific technique to find out the prey’s location as well as obstacles. 

Seismic P-waves

The seismic-P waves move at the highest speeds out of the waves in the form of elastic motions. They are one of the examples of longitudinal waves that can travel by both liquid and solid materials in the interior of the Earth. With seismic-P waves, the medium’s particles tend to vibrate in a way that resembles sound waves. Here, the transmitting channel is alternately expanded and compressed. The S wave, a slower form of body wave, transmits only via solid material. With S waves, the motion of the particle is transverse to the travel direction. 

Conclusion

The topic of longitudinal waves is essential in physics as well as for exam preparations. Hence, here we try to provide the most essential key details on the longitudinal waves. Here we learned the definition, formula, and questions regarding different types of longitudinal waves.