Refraction and Diffraction

[BoMan]

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One of the things I love about surfing is its complexity. There’s always something new to learn about my favorite spot. The waves diffract around Duxbury reef and refract on the rocky shallows. As a goofy footer, I need a rising tide, a long period and at least 3 foot waves to bring my left break alive. Does this affect you?

Surfline forecaster Katie Jackson explains the difference.

Refraction - As a wave travels from deep to shallow water, the wavelength shortens, the wave speed slows down, and the wave will refract, or bend, toward the shallow area in order to conserve its energy.

Diffraction - Diffraction occurs when a wave encounters an obstruction in its path and will change direction, or wrap around it. In ocean waves, we see this occur when a wave encounters an object like a jetty and the wave rotates around it.

http://www.surfline.com/surf-science/refraction-vs-diffraciton---forecaster-blog_14984/

[jaffa1949]

I have a reaction your action
Posting a distraction
Of refraction
And diffraction..

It is rather shallow to bend a wave, or bend around a rock or pier.

Can make the shape a little queer.
But these are actions can produce a
Noosa
Or follow through a Malibu.
To Raglan in New Zealand
Or just Indo with a G Land.

The long sandy shores
That bending ignores
and makes good waves so rare, Oh!
Frustrating the likes of our PMCaero.

[oldmansurfer]

The breaks I surf on the east side of Kauai will sometimes catch a refraction from a north swell or a south swell. sometimes it is just mixed in with the wind swell or sometimes by itself when there isn't the usual tradewinds. However I am happy with wind swell....any swell is good for me but some are better than others