Dispersion of Water Waves on Stockton Lake, Missouri

April 02, 2015

Waves

Photographer: Tommy Hornbeck
Summary Author: Tommy HornbeckApril 2015 Viewer's Choice

If you stand on the shore of a lake or on an ocean beach and watch the waves roll in it seems that the water is moving shoreward. Oddly enough, however, the water rarely seems to pile up as it reaches shore. This is because the water itself isn't moving, except in a small, more or less circular pattern. For a fixed water depth, surface waves of different frequencies travel at different speeds, with the longer wavelengths traveling faster than the shorter wavelengths. Most waves are created by the action of the wind, but the ones shown above were created by the fisherman's speeding boat in the left photo. 

Left photo - On a relatively calm day, the boat passed by at 1:06 p.m.

Center photo - Two minutes later the lower frequency waves (longer wavelength) reach the shore well ahead of the still distant, higher frequency waves.
 
Right photo - Finally, after three and a half minutes, the higher frequency waves reach the shore. The water then returned to a calm state. Photos taken on January 30, 2015.

Photo details: Nikon D7100 camera; 1/400 sec. exposure; F/10; ISO 400; focal length 22mm.