# How to visualize the amplitude of a longitudinal wave?

Sound is a longitudinal wave. Loudness of the sound depends upon its amplitude, but I was thinking how to visualize the amplitude of a longitudinal wave. In case of a transverse wave its easy but in case of longitudinal I have difficulty visualizing the amplitude. Any help will be deeply appreciated. Thanks!

## 3 Answers

For a longitudinal wave the amplitude is again the maximum deviation of a single particle from its equilibrium position.

The animation below (from Physics Lens - Longitudinal and Transverse Waves) visualizes this for a longitudinal and for a transverse wave. Keep your eye on the moving spots marked in red.

• Commented Jan 14 at 13:34

The visualization of the amplitude in a longitudinal wave typically involves an examination of the number of compressions and rarefactions within the wave diagram. As universally acknowledged, the height of the peak serves as an indicator of the loudness or amplitude in a transverse wave. Analogously, within the context of a longitudinal wave diagram, the quantity of compressions and rarefactions holds a direct and proportional relationship with its amplitude. Here is a diagram for better understanding:

An alternative perspective involves considering the illustration of a sound wave. Classified as a longitudinal wave, a sound wave manifests compressions and rarefactions, emanating from the periodic compression of air molecules. Amplification in the quantity of these compressions and rarefactions directly correlates with an escalation in the volume of the sound. This augmentation results from the heightened magnitude of each compression and rarefaction, consequently yielding a more pronounced and discernible acoustic effect.

Here are some HTML5 visualizations of transverse waves by Andrew Duffy (Boston U.) https://physics.bu.edu/~duffy/sims.html .

See also the PhET Waves Intro (choose Sound for a longitudinal wave)
https://phet.colorado.edu/sims/html/waves-intro/latest/waves-intro_en.html

(Click on the thumbnails for a full sized picture.)