Physics/Why water reflects -- and nanotech
I was wondering if in nano technology of water there is an application or rather a way to harness the reflective properties of the water molecule or a water molecule for technology purposes. one expert told me it take s more then one water molecule to reflect images the other told me different the one that told me different is maxed out.I would like to go back to chool to study nano technology. where in the water molecule does it reflect images I realize of course this takes light.and with sound or vibration could images be made duplicated or real using water as the relector?thanks .
I agree with the second expert -- of course, why choose me as opposed to the first expert? Permit me to explain why I reach my conclusion.
Water reflects incident light for the same reason that metals reflect light -- there is a lot of free moving charge in both. In metals, it is the electrons, basically roaming around the crystal. In water, it is the dipole moment of the water molecule.
In both cases, the electromagnetic wave (EM wave; ie, the light) strikes the charged particle, causing it to vibrate in sync with the wave. When a charged particle vibrates, it gives off an EM wave of the same frequency as its vibration. In THAT sense, each individual molecule of water "reflects" light.
Notice, however, that a single molecule, vibrating because of the EM wave impinging on it, would re-radiate light in all directions. So why does light come off from water in only ONE direction? Indeed, why does the EM wave come off the water at an angle exactly equal to the angle that the light came upon the water?
This can only be explained by rigorously looking at the re-radiated EM waves from ALL the water molecules (or all the metal's electrons). From a classical viewpoint, adding up the strength of the E-field from all such re-radiated EM waves and taking into account the phase difference between all such waves, you get total destructive interference for all waves EXCEPT those coming at exactly the angle of incidence.
OR you could approach the situation using quantum electrodynamics -- which is more precise but a LOT more difficult to follow. When a photon is incident on a dipole (like a water molecule) or a free electron (like in a metal), it has a certain probability of scattering in various directions. When you add the probabilities of ALL photons being scattered at a specific angle by ALL dipoles, you get that the only significant angle of reflection is exactly equal to the angle of incidence. It's POSSIBLE for a photon to not reflect at that angle, but it's vanishingly UNLIKELY.
Okay, so is there any nano-technology that can advantage of what we've just described? Not that *I* can think, but I don't have a lot of imagination for nano-technology. Fortunately, clever students today can think of ideas that would never occur to me.