August 26, 2022

Breaking Wave

On "our" lake in northern Vermont (Willoughby Lake) where we have been all summer we are often treated to a morning of a fair wind with the moderate waves breaking on the beach shore.  These waves were about 0.3 meters high (about 1 foot).  As the waves reach the beach, the base of the wave becomes blocked by the shallower bottom of the lake, but the top of the wave keeps moving, until there is no water beneath the crest of the wave.  The wave curls abruptly and comes crashing down onto the beach in what is called a "curl".

I used the "slo-mo" feature on my smart phone to capture the breaking wave in slow motion, which plays back repeatedly in the video clip below.

 
 
This clip shows the curl crashing onto the beach in the center of the photo.  Notice that when the curl breaks, a tube of air is trapped as a cylindrical cavity in the center of the curl.  Notice that after the curl crashes, the trapped air rapidly escapes the crest of the breaking wave and erupts directly behind the crashing curl front as a row of miniature fountains.  The left part of the image did now exhibit the curl, but the top of the wave slid forward from the base as a cascade rather than as a steep-sided curl and fails to trap air. 
 
The open ocean experiences much larger waves than this medium sized lake.  The far shore from where the waves originate is only about 3 miles distant.  Experienced surfers get their biggest thrills on the oceans riding the curling breakers as they approach a beach.  Dangerous - especially if the wave crests are higher than the surfer's height!  

Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department. These photos feature interesting phenomena in the world around us.  Students, faculty, and others are invited to submit digital (or film) photographs for publication and explanation. Atmospheric phenomena are especially welcome. Please send any photos to dcollins@warren-wilson.edu.

All photos and discussions are copyright by Donald Collins or by the person credited for the photo and/or discussion.  These photos and discussions may be used for private individual use or educational use.  Any commercial use without written permission of the photoprovider is forbidden.

Observers are invited to submit digital photos to:



 

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