Main Difference – Transverse vs. Longitudinal Waves
Transverse and longitudinal are two different types of waves. The main difference between transverse and longitudinal waves is that in transverse waves, oscillations occur perpendicular to the direction of propagation of the wave, whereas in longitudinal waves, oscillations occur parallel to the direction of propagation of the wave.
What are Transverse Waves
In transverse waves, the oscillations take place perpendicular (normal) to the direction of propagation of the wave. A simple demonstration can be performed by wiggling a rope up and down. The wave itself will propagate along the rope whereas the individual particles in the wave oscillate perpendicularly to the rope’s length.
The wave in the above example is a mechanical wave—the wave passes through a medium (the rope) whose particles oscillate to conduct the wave. In addition, transverse waves include electromagnetic waves as well (radio waves, microwaves, infrared, visible light, ultraviolet, x-rays and gamma rays are all electromagnetic waves). Electromagnetic waves do not require a medium to propagate in, i.e. they can travel through a vacuum. We get energy from the Sun through electromagnetic waves emitted by the Sun. In electromagnetic waves, there is no particle that physically oscillates to propagate the wave through space, but rather, it is an electric field and an accompanying magnetic field that oscillate.
Oscillations of a transverse wave could be set up in any direction perpendicular to the direction of propagation. When all the vibrations are occurring along one direction, the wave is said to be polarised (polarized).
What are Longitudinal Waves
In longitudinal waves, oscillations occur parallel to the direction of propagation of the wave. The most common example for these types of waves is sound waves, which consist of oscillating air molecules. The parallel motion sets up regions with compressions where the oscillating particles are closer together, and regions with rarefactions where the oscillating particles are further apart.
Since longitudinal waves can only oscillate along one direction, they cannot be polarised. The diagram below illustrates the difference between transverse and longitudinal waves:
a) On top: A longitudinal wave and b) at the bottom: a transverse wave.
Difference Between Transverse and Longitudinal Waves
Direction of Oscillations
In transverse waves, oscillations take place perpendicular to the direction of propagation of the wave.
In longitudinal waves, oscillations take place parallel to the direction of propagation.
Polarisation
Transverse waves can be polarised.
Longitudinal waves cannot be polarised.
Image Courtesy:
“ Direction of oscillation and propagation of a longitudinal wave (a) and a transverse wave (labels in German)” by Debianux (Own work) [CC BY-SA 3.0], via Wikimedia Commons (modified)
