An observer on the beach always sees larger waves come in directly toward him, with the wave crests parallel to the shore, even though some distance out from shore they are seen to be approaching at an angle. What makes the waves straighten out?

Question

osprey · Answer

Ripple tank shows this. Ripples generated by a small source have circular wave fronts. As they spread out, the circles' circumferences get bigger, and part of the circle - on the beach - could seem to be a straight line. Straight lines have parallel crests and troughs, not so with circulars, which are concentric. I think that's right, and I hope that it is. http://perendis.webs.com

ljetibo · Answer

http://openstudy.com/study#/updates/57dd56cee4b022b6aff27d9f It could also have to do with the fact that the dept changes drastically as you get closer and closer to the shore which makes waves turn parallel to the coast. Of course this would probably require a gentle slope that gets shallower and shallower. I've often seen waves come at an angle to the shore. I'm more familiar, in my life/experience, with the steeper rocky shores though.