Total internal reflection
Have you ever wondered why at some angles the sea looks blue (or whatever the color of the sky that day) and at others you can actually look into the water? That’s the phenomenon of total internal reflection. There is a critical angle at which you switch from “being able to look into water” to “total internal reflection”, i.e. the sky being reflected off the water’s surface and reaching your eye. Below you see a nice example of this: The more perpendicular you look at the water surface (i.e. those sides of the wave facing you), the better you can look into the water. Whereas all those parts of the sea surface that face away from you look blue and you can’t look into the water there.
I think this is totally fascinating! Don’t those pictures look almost fake?
And, btw, this doesn’t only happen if you look in parallel to the direction of wave propagation. Although it looks even weirder at an angle:
Can you see how all those tiny ripples on the wave each show the same phenomenon of either reflecting the sky or being transparent and showing the sea floor underneath? How cool is that? :-)
Commissioned wave watching: Eckernförde edition on a beautiful calm and sunny Sunday! | Mirjam S. Glessmer says:
[…] into the water in the foreground but not in the background? That’s the awesome phenomenon of total internal reflection where, if you look at water at an angle that is smaller than a critical angle, you cannot look […]
Wave watching by proxy — looking at how waves focus light on the sea floor | Mirjam S. Glessmer says:
[…] But this only happens if we look at water at a small angle — then the water surface acts to reflect most of the light from above. However if we look at water at a steep angle, we are actually able to look inside. See this in the picture above? This is due to a phenomenon called total internal reflection. […]
Saturday morning #wavewatching | Dr. Mirjam S. Glessmer says:
[…] And in that picture there is so much to see: different surface roughnesses where a breeze creates ripples and where there is no wind, reflection changing depending on the surface roughness, and, favourite topic of mine, total internal reflection! […]
The perfect wave — and why this is not a fake image | Dr. Mirjam S. Glessmer says:
[…] we can look into the water and see the jungle beneath the waves: this is due to a phenomenon called total internal reflection. Spooky, isn’t […]
Wake watching at Ratzeburger Segelschule | Dr. Mirjam S. Glessmer says:
[…] due to a phenomenon called “total internal reflection“: For light that hits the interface between two different materials (air and water in this […]