Obviously I know why the sea is blue. I am unsure as to the process by which light is absorbed. Usually absorption, reflection and transmission occur via the interaction of photons with electrons, but as I understand it this occurs in water only at UV wavelengths. Absorption and reflection of visible light in water is the result of harmonic vibration. How exactly does this process work? It energy transfer to the proton facilitated by the nucleus?
In optics classes they give wonderful explanations about why the sky is blue, because it’s relatively straightforward Rayligh Scattering, and the explanation is instructive and easily grasped.
They do a much worse job of explaining why snow shadows are blue or why water is blue. Both are due to different types of Multiple Scattering effects, and the development is not simple and straightforward, and is kinda messy.
Here’s an article on why water is blue due to multiple scattering
http://www.dartmouth.edu/~etrnsfer/water.htm
Actually, I don’t make it clear – they generally don’t even try to explain why ice or water is blue. If you want to find out why, you have to dig out journal artcles on your own.
Well it seems from the link you provided that it is indeed caused by interaction between the photon and molecule. It’s all so much more complex than simple particle physics.
Of course it’s due to interaction between the photon and the molecule – All scattering is interaction between the photon and the molecule, including the scattering responsible for the sky being blue.
What’s complicated here is that you have to consisder light that scatters first from one molecule, then another, then another. Rayleigh scattering from widely-separated air molecules can, to good appreoximation, be treated as a single scattering from a single molecule.
No, no… You misunderstand. Most light scatters are a result of interaction with electrons specifically. In glass for instance, light hits the glass, that light is largely absorbed by electrons in the glass, passing their energy to the electron and causing it to enter an excited state. The electron then settles to a lower energy state and emits a photon, and so on through the glass. In other substances the photon interacts with the electron to produce heat (a matte black surface for example). Water is a special case, where it’s not the electron, but the molecule itself that causes the color shift.
I’m afraid you misunderstand – lightr scatters from air molecules and water molecules, as well as from oil droplets, smoke, and other random stuff. Any time light strikes a substance you’ll get, in general, some absorption, some transmission, and some refdlection. Sometimes it interacts with molecules, but if light is seen as interacting with the electrons of the glasa or whatever, it’s interacting with the electrons of the molecule, too. It’s not as if there’s a fundamentally different interaction with scattering from particles or a vast chuck of water than there is with light interacting with glass.
Taken from the link you posted:
To our knowledge the intrinsic blueness of water is the only example from nature in which color originates from vibrational transitions. Other materials owe their colors to the interaction of visible light with the electrons of the substances.
The vibrational transitions mentioned are caused by hydrogen bonding. Clearly the mechanism for the “blueness” of the ocean is different than that of the blue paint on a car, or the blue colour of the sky. I am just not sure how the process works. Photon-electron collisions I understand. Ionizing radiation I understand. Neutron bombardment I understand. And yet I am stumped as to why the sea is blue.
But even in the case of vibrational transitions, the photons are interacting with the electrons – it’s just a matter of how they do it.
Because of the reflection from the sky, which is blue. I learned that in one of the Edgar Rice Burroughs “Pellucidar” series.
A slight digression, but I always thought deep blue sea referred to, well, depth, rather than colour.
Edit - according to this it seems the sea was originally just deep, and blue was added later.
And before that, it was “wine-dark.”
Whoosh?
The colour of the sky contributes (on a clear day). But water is also blue.
I don’t think so. On further investigation it seems light behaves as a wave, and interacts with the molecular force field. The vibrations in the molecular force field of water happen to be at the frequency needed to alter the wavelength of light to the blue visible spectrum.