Waves are defined as oscillations around a fixed point that occur as energy moves from one medium to another. A mechanical wave is the kind that results from oscillation-induced energy transfer across a medium. Mechanical waves can be divided into two main categories: Transverse waves and longitudinal waves. Before knowing the difference between transverse and longitudinal waves, let us have some information on waves and their types.
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What is Wave?
A wave is a disturbance that moves energy from one location to another without carrying any material. A stone strikes the water’s surface and causes ripples that travel in the shape of concentric circles with their radius rising until they reach the pond’s boundary. Waves are classified into two types: longitudinal and transverse.
Transverse Wave
Transverse waves are mechanical waves in which the motion of the medium’s particles is perpendicular to the direction of propagation. This indicates that in transverse waves, particle movement is perpendicular to energy movement.
A transverse wave is best exemplified by waves formed in string. Transverse waves have crests and troughs. The peak is the wave’s crest or top point, while the trough is the wave’s valley or bottom. Standing waves are created by stringing together waves.
Imagine you’re holding one end of a rope and giving it a strong upward flick. The bump or wave goes horizontally as the rope moves up and down, forming a transverse wave.
Light waves are electromagnetic waves, which are all examples of transverse waves.
Visual Representation of Transverse Waves
When a pebble is put into still water, it causes ripples that spread outward in concentric rings. If you look closely at any point on a ripple, you will observe that the water travels up and down as the ripple moves outward. The water particles’ upward and downward movement is perpendicular to the ripple’s outward motion.
Crests and Troughs
A transverse wave has two main features: crests and troughs.
- Crests are the highest points when a medium (such as water or rope) reaches its maximum height.
- The trough is the lowest point where the surface drops down. The wavelength of a wave is defined as the distance between crests or troughs.
Examples of Transverse Waves
- Light is one of the most prevalent types of transverse waves. While we cannot observe the actual oscillations of light waves, they do move in a transverse direction.
- Another concrete example is a guitar string. When plucked, the string vibrates up and down, forming a transverse wave that generates sound. This upward and downward motion is perpendicular to the direction in which the wave travels along the string.
Longitudinal Wave
In longitudinal waves, particles transfer energy from one location to another by vibrating in the direction of the wave’s propagation. The movement of particles in longitudinal waves is usually parallel to that of energy.
The particles are also shifted in the same direction as the traveling wave. Longitudinal waves are represented by compressions going along a slinky. Pushing and pulling the slinky horizontally allows us to create a longitudinal wave.
Longitudinal waves travel in compression and rarefaction. Sound waves are the most obvious example of longitudinal waves.
Visual Representation of a Longitudinal Wave
Visualize a slinky toy. When you compress a few coils at one end and then release them, a bunching and spreading effect occurs down the length of the slinky. This clumping and spreading motion, which occurs in the same direction as the disturbance, is a longitudinal wave.
Compression and Rarefaction
Compressions and rarefactions are key ideas for comprehending longitudinal waves.
- Compressions are areas where particles in a material are closer together or more bunched together. In the slinky example, compressions are locations when the coils are close together.
- Rarefactions are places where particles are spread out or have a lower density. Rarefactions are stretches of the slinky’s coils that are spaced farther apart.
These longitudinal wave characteristics are similar to the crests and troughs seen in transverse waves.
Example of Longitudinal Waves
The most common example of a longitudinal wave is sound. When something creates a noise, it causes vibrations (or pressure changes) in the surrounding air. As these vibrations travel, they cause air molecules to group in compressions and split apart in rarefactions. The back-and-forth motion of molecules in the direction of the sound allows humans to hear sounds, whether they are songs on the radio or the chime of a bell.
Difference Between Transverse and Longitudinal Wave
One significant distinction between longitudinal and transverse waves is the direction in which individual particles or fragments of the medium move in reaction to the wave’s passage.
| Transverse Wave | Longitudinal Wave | |
| Definition | In transverse waves, particles transfer energy from one location to another by vibrating perpendicular to the wave’s propagation direction. | Longitudinal waves occur when particles in a disturbed medium shift in a direction parallel to the wave’s propagation direction. |
| Components | Crests and troughs | Compression and rarefaction |
| Direction of Motion | Perpendicular to the direction of particle movement | Parallel with the direction of particle motion |
| Movement of particles | Particles travel up and down in the medium. | Particles move back and forth in the medium |
| Effect of movement | The movement of particles causes vibration in other particles | The movement of particles leads in horizontal wave expansion. |
| Polarization | Can be polarized | Cannot be polarized |
| Energy Transfer | Energy transmission occurs perpendicular to the wave motion | Energy is transferred in parallel with the wave motion. |
| Speed | Speed varies with medium qualities and wave frequency | Speed is solely determined by the qualities of the medium. |
| Alignment | Alignment is possible | No alignment is possible |
| Medium | It can only be obtained in solid or liquid form. | It exists in all three mediums: solid, liquid, and gas |
| Examples | Light, electromagnetic, and surface water wave | Sound waves, seismic waves, and compression waves in springs. |
Similarities Between Transverse and Longitudinal Waves
- Both transverse and longitudinal waves are mechanical waves, which means they need a medium to travel. Both involve energy transfer via particle oscillations in the medium.
- The speed of transverse and longitudinal waves is determined by the qualities of the medium through which they travel. It is determined by the medium’s elasticity and density.
- Both longitudinal and transverse waves have a wavelength and frequency. The number of oscillations per unit of time can differ between these two types of waves.
- When waves interact with different media, they can be reflected or refracted.
Video on Transverse vs longitudinal wave
References
- https://byjus.com/physics/difference-between-longitudinal-and-transverse-wave/
- https://byjus.com/jee/longitudinal-and-transverse-waves/
- https://www.toppr.com/guides/physics/difference-between/longitudinal-and-transverse-wave/
- https://www.ck12.org/flexi/physical-science/longitudinal-wave/what-is-the-difference-between-transverse-and-longitudinal-waves/
- https://www.tutoroot.com/blog/what-are-longitudinal-and-transverse-waves-difference-diagram/
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- https://www.studysmarter.co.uk/explanations/physics/waves-physics/longitudinal-and-transverse-waves/
- https://www.geeksforgeeks.org/difference-between-longitudinal-and-transverse-waves/
