# What is Longitudinal waves: Definition and 47 Discussions

Longitudinal waves are waves in which the vibration of the medium is parallel to the direction the wave travels and displacement of the medium is in the same (or opposite) direction of the wave propagation. Mechanical longitudinal waves are also called compressional or compression waves, because they produce compression and rarefaction when traveling through a medium, and pressure waves, because they produce increases and decreases in pressure. Sound travels through longitudinal waves. Sound travels through transversal waves in 90 degrees.The other main type of wave is the transverse wave, in which the displacements of the medium are at right angles to the direction of propagation. Transverse waves, for instance, describe some bulk sound waves in solid materials (but not in fluids); these are also called "shear waves" to differentiate them from the (longitudinal) pressure waves that these materials also support.
Longitudinal waves include sound waves (vibrations in pressure, a particle of displacement, and particle velocity propagated in an elastic medium) and seismic P-waves (created by earthquakes and explosions).
In longitudinal waves, the displacement of the medium is parallel to the propagation of the wave. A wave along the length of a stretched Slinky toy, where the distance between coils increases and decreases, is a good visualization and contrasts with the standing wave along an oscillating guitar string which is transverse.

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1. ### I Understanding the propagation of sound on molecular Scale

I am actually an undergraduate in Physics but I didn't understand this basic phenomenon. I saw this youtube video today and I was wondering how molecule in air would be able to regain it's initial position after it has transferred it's energy to the adjacent particle. Is it like a rebound, it...
2. ### Direction of of the velocity vector for particles in a sound wave

Using the equations mentioned under this question, I came up with following analysis and directions of velocities on either side of ##x_1##. Also, I'm not sure if there is an easier qualitative way to know the velocity directions rather than do a detailed Calculus based analysis?

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4. ### I Longitudinal waves on a string

Good day to everyone, I kindly ask for your help. My question is: "Does a string have to be under tension, to transmit longitudinal waves? Why is it so?" I have trouble finding relevant scientific articles regarding the question and for reasearching "longitudinal waves on a string". If anyone...
5. ### B Why longitudinal waves are waves?

i know it's an absurd question, but why are longitudinal waves called waves although they aren't wave-like?
6. ### Extension of a rod segment dx due to a passing longitudinal wave

Let us look at short segment of a rod with its length dx. Due to longitudinal wave, left endpoint moves for s in the direction of x-axis and the right endpoint moves in the same direction for s+ds. Because I want to calculate the elastic energy of the wave motion, I need the extension of dx so...
7. ### I Amplitude of particles in the medium of a longitudinal wave

I was thaught you can create a sinusoidal wave by making a source oscillate with simple harmonic motion in a medium, such as moving one end of a rope up and down to create a periodic transverse wave. For transverse waves, it is easy to see that every particle in the rope moves up and down with...
8. ### Writing: Input Wanted Longitudinal Waves: Do Devices Use AM or FM?

Do longitudinal wave devices use AM or FM?
9. ### I Longitudinal Waves: Compression & Rarefaction

In a longitudinal wave is a compression pulse always followed by a rarefaction on its tail
10. ### How is longitudinal wave spread

Homework Statement How is longitudinal wave spread? http://s11.postimg.org/pm7hxibo3/vala.png Here is how the transverse wave is spread in T/4, T/2, 3T/4, T (T- period) I need the same graph for the longitudinal wave. Homework Equations X=c*T (c-velocity of moving of the wave) The Attempt at...
11. ### Young's equation and longitudinal waves

Hi I have learned at school that we can use Young's equation Lambda = ax/D to calculate the wavelength of light from an interference pattern I'm wondering if this equation also works for longitudinal waves? Thank you for your help
12. ### Longitudinal waves and vector potentials.

Hello, I was wondering if anybody knew of any material (books, papers etc..) which considers a possible connection between longitudinal waves and vector potentials, at least mathematically. I have been scouting about, but failed to find anything substantial. I understand that there seems to be...
13. ### I Way of producing 600kHz longitudinal waves - Piezo or siren

Hello! My name is Nick and I have an MSc in Computer Science, I'm also Physics enthusiast and amateur/independent researcher. I would like to ask for your help on something. I'm currently trying to find a way to study ultrasonic waves' effects on water and I'd like to find a means of...
14. ### Mechanical / progressive / transverse / longitudinal waves

Correct me if I'm wrong, but based on what I've learnt, there are three kinds of waves: mechanical, transverse progressive and longitudinal progressive. Mechanical - A disturbance makes particles vibrate on the spot Transverse progressive - Energy is carried, and moves perpendicular to the...
15. ### Maxwell's equations and longitudinal waves

Hi guys, I am having hard times in understanding whether or not the longitudinal electromagnetic waves are solutions to Maxwell's equations. In Cohen-Tannoudji "Introduction to QED" it's stated that by writing the fields as the sum of a longitudinal and transverse part one can show that waves...
16. ### Choose the correct snapshot graph longitudinal waves

Homework Statement http://i.imgur.com/4dL6TQY.jpg I don't know how to read the figure or the graphs. O_O
17. ### Longitudinal waves in a quartz plate

Homework Statement In a quartz longitudinal waves produce peaks on the 2 sides of the plate. the base frequency is: ##f_1=\frac{2.87E5}{s}## Where s is the thickness. calculate Young's modulus of quartz. \rho=specific mass=2.66[gr/cm3] Homework Equations \lambda=wavelength, u=velocity...
18. ### Calculating Time Difference of Longitudinal Waves in Steel Pipe

Homework Statement A steel pipe of length 60m is hit at one side. a man standing at the other side hears 2 sounds, one that passes in the pipe and one through the air. what is the time difference. Take the modulus of elasticity as 2,180,000[kgf/cm2] Homework Equations Velocity in the...
19. ### Transverse and longitudinal waves

let me make it clear this is NOT A HOMEWORK.i am just having a doubt. if there is a rope passing through two parallel vertical slits placed close to each other. The rope is fixed and if it's moved up and down perpendicular to its length,transverse waves are generated with vibrations parallel...
20. ### Surface waves vs longitudinal waves

in fluid only longitudinal waves propagate but in Ocean water both transverse and longitudinal waves propagate. Does that mean Ocean water is not a fluid? I am confused. Can anyone explain please.(Longitudinal wave is the evidence for Earth core is liquid)
21. ### Wave Equation applied to a spring with longitudinal waves?

Homework Statement A spring of mass m, stiffness s and length L is stretched to a length L + l. When longitudinal waves propagate along the spring the equation of motion of a length dx may be written pdx second partial derivative of n with respect to t = partial derivative of F with respect to...
22. ### Longitudinal Waves in Air (Experimentally determining the speed of sound)

Problem: In my physics class, we conducted an experiment involving a column of air set vibrating by a tuning fork of a known frequency f held at the upper end. The wave travels from the source to a fixed end (namely the water in the lower end of the tube) & reflected back to the source...
23. ### Longitudinal Waves - are they very different?

Homework Statement A continuous sinusoidal longitudinal wave is sent along a coil spring from a vibrating source attached to it. The frequency of the source is 25vib/sec, and the distance between successive rarefactions in the spring is 24cm. a) Find the wave speed b) if the max...
24. ### Pushing solid objects and longitudinal waves

Hi All, I am still trying to wrap my head around the five light year stick and the idea that if you push an object, it moves because longitudinal waves of compression force (?) are sent through the medium of whatever the object is made of: https://www.physicsforums.com/showthread.php?t=386687...
25. ### How does density affect pressure in longitudinal waves?

In my textbook they have introduced the concept of longitudinal waves and go on to explain what a compression and what a rarefaction is.It is written- "In a compression, there is a temporary increase in the density of the medium; and in a rarefaction,there is a temporary decrease in the density...
26. ### Compressions and Rarefactions in longitudinal waves

I know this may seem quite trivial but I just want to make sure, do the compressions in a longitudinal wave represent the highest displacement, in a transverse wave this is known as the crest, and do rarefactions represent the equivalent of troughs in longitudinal waves? Thank you in advance
27. ### Wavefronts and Longitudinal Waves Displacement-Time Graph

Hi, I am studying waves and I am having a hard time understanding the following concepts: Wavefronts: I understand the principle. The only thing confusing me is when my teacher was explaining, he drew a light ray and lines perpendicular to that ray and he said those were the crests of the...
28. ### Wave Encyclopedia: Examples of Transverse & Longitudinal Waves

As I'm sure many of you know, waves can be either transverse or longitudinal. Transverse waves involve vibrations that are perpendicular to the propagation (direction of motion) of the wave, and longitudinal waves' vibrations are parallel to the wave's propagation. Electromagnetic waves such...
29. ### Velocity of Longitudinal Waves

Does the formula for velocity of the wave = wavelength * frequency hold true for longitudinal waves (like sound wave) also? If yes then we don't find the velocity of sound by any such formula. Moreover, is the wavelength and frequency defined for longitudinal waves?
30. ### Longitudinal waves have a crest or not ?

longitudinal waves have a crest or not ? I am not sure.
31. ### Electron double-slit experiment transverse or longitudinal waves?

In the case of the double-slit experiment using electrons, what kind of interference pattern is created? Characteristic to transverse or longitudinal waves? Can we tell only analyzing the interference pattern what type of waves created it? Thanks!
32. ### Velocity of longitudinal waves in a solid.

Homework Statement Our lecturer gave us a general equation for velocity of waves; (where c= wave velocity) c= \sqrt{\frac{\textrm{springiness}}{\textrm{massiness}}} (Excuse the terms, I'd personally rather have been given the equations here..) So for transverse waves on a string/wire...
33. C

### Determine the speed of the medium in transverse and longitudinal waves.

Homework Statement In the situations where a transverse or longitudinal wave is propagating through a medium, the medium moves. How do you determine the speed of the medium's motion? When is the medium's speed at a maximum? Homework Equations The speed of the propagating wave is v = frequency...
34. ### Longitudinal waves in a clamped metal rod

Homework Statement The speed of sound in a metal rod is 3600 m s -1. The rod is 1.20m long and clamped at one of its ends. (a) Determine the frequency of its vibration if longitudinal waves are established in the rod and it is vibrating in its first overtone mode. (d) Determine the...
35. ### Calculate Speed and Time of Longitudinal Wave in 6m Spring

Homework Statement a longitudinal wave in a 6.0m long spring has a frequency of 10.0 Hz and a wavelength of 0.75m. calculate the speed of the wave and the time that it would take to travel the length of the spring. Homework Equations v = f (wavelength) The Attempt at a Solution v =...
36. ### Longitudinal Waves (Heart Wall of unborn)

Homework Statement A vet is using an ultrasonic motion detector to detect the heartbeat of an unborn chimp baby and claims that the speed of sound in the soft tissue of a chimp should be 1489 m/s. According to the manual which comes with the motion detector, the emitted frequency of sound...
37. ### Transverse vs. Longitudinal Waves

Homework Statement Please explain the difference and try to give examples. I know that the displacement of the medium in a transverse wave is perpendicular to the direction of wave travel and in longitudinal is parallel to the direction of wave travel, but does this mean that transverse waves...
38. ### Longitudinal Waves: Compression or Rarefaction at Displacement 0?

Why is it that when a longitudinal wave is represented by a (pressure/position) and a (displacement/position) graph does the displacement 0 represent a compression or rarefaction (maximum or minimum pressure)?
39. ### Explaining Low Frequency and Longitudinal Waves in Fluids

seeking help..please why do low frequency contributes a low pitch?how?& why only longitudinal in fluids?can any1 please explain to me,tq please..:smile:
40. ### Longitudinal Waves Help Wanted

I know that when a Longitudinal (Sound) Wave spreads in water the displacement of the water particles is parallel to the direction of wave propagation and the displacement equation looks like this : y(x,t)=A*sin[2*π*f*(t-x/u)] where : A=Amplitude, π=3.14..., f=frequency, u=speed...
41. ### How Do Longitudinal Waves Behave on a Taut String?

Hi guys, this is Barton Zwiebach's Introduction to String theory question 4.2 on the longitudinal wave on a taut string. The problem is purely classical and I seem to obtain a solution which seems far too complicated for me. If anyone has the answers it would be great, if not just your help...
42. ### Why can’t longitudinal waves be polarized?

Why can’t longitudinal waves be polarized? I’m guessing its something to do with the particles oscillating in the same direction of propagation, but I can’t think of a explanation of why they can’t be polarized. I have also been told that some transverse waves can’t be polarized. X-rays can...
43. ### Conceptual question about longitudinal waves

So we are working on sound waves in my physics course now and I was doing some textbook reading. I have been following it pretty well, but I just came across a relationship that I am not quite following. It is with reference to wave interference. Let us say that two sound waves are emitted...
44. ### Transverse longitudinal waves : slinky lab

transverse longitudinal waves : slinky lab! so this lab we did is called the transmission and reflection of a one-dimensional transverse wave... 1. we created a transverse pulse from one side and observed a point near the middle of the spring as the pulse passed... - > so i wrote that it just...
45. ### Distinguishing property of Transverse and longitudinal waves

Sir, It is said that it is possible to distinguish between transverse and longitudinal waves by studying the property of polarization. Also it is said that longitudinal waves cannot be polarized but transverse waves can be polarized. Are they true?
46. ### Longitudinal waves in circuits?

hello im just confusing about the electrical conduction in the electrical circuits I mean, for example, -an alternate voltage means that the electrons move back and forth in the circuit? -if really this happens, then the electric waves in the circuit are LONGITUDINAL, because by definition...
47. ### Longitudinal waves, thickness of an element

I'm confused by something my book says. For reference, here is the relevant text: Figure 18-5b shows an oscillating element of air of cross-sectional area A and thickness \Delta x, with its center displaced from its equilibrium position by a distance s. From Eq. 18-2 we can write, for the...