Thursday, August 19, 2010

A virtual rainbow

   Many time I have been watching the feeds of the ROV cams, only to see so many different lighting types, but also different colors, I'm sure you have too....

I have my theory about the different colors, I thinks it's basically caused by sonar. I'll explain with a few simple excerpts from Wikipedia.

                                         Raman scattering or the Raman effect

    In 1922, Indian physicist C. V. Raman published his work on the "Molecular Diffraction of Light," the first of a series of investigations with his collaborators which ultimately led to his discovery (on 28 February 1928) of the radiation effect which bears his name. The Raman effect was first reported by C. V. Raman and K. S. Krishnan, and independently by Grigory Landsberg and Leonid Mandelstam, in 1928. Raman received the Nobel Prize in 1930 for his work on the scattering of light.

    When light is scattered from an atom or molecule, most photons are elastically scattered (Rayleigh scattering), such that the scattered photons have the same energy (frequency) and wavelength as the incident photons. However, a small fraction of the scattered light (approximately 1 in 10 million photons) is scattered by an excitation, with the scattered photons having a frequency different from, and usually lower than, the frequency of the incident photons. In a gas, Raman scattering can occur with a change in vibrational, rotational or electronic energy of a molecule . Chemists are concerned primarily with the vibrational Raman effect.

The Raman effect differs from the process of fluorescence. For the latter, the incident light is completely absorbed and the system is transferred to an excited state from which it can go to various lower states only after a certain resonance lifetime. The result of both processes is essentially the same: A photon with the frequency different from that of the incident photon is produced and the molecule is brought to a higher or lower energy level.

But the major difference is that the Raman effect can take place for any frequency of the incident light.

                      Here's some various minerals under the effect, beautiful...


    So lets say that a certain wavelength of sonar was being used in front of an ROV,. The ROV is using the sonar, and at the same time, lighting the area and filming simultaneously. There are many things suspended in the water around the well, everything from heavy ppms of various minerals, to COREXIT ( there is an autonomous dispersant system in use on the seafloor, it's in the official BP press release documents. ) to dispersed oil, etc etc, I'll skip a long-winded list, I'm sure you get the idea. . So....sonar.....suspended particulates, ultrasonically attenuated light and fluorescing minerals and compounds....seems fairly simple to me.


The frequency of light scattered from a molecule may be changed based on the structural characteristics of the molecular bonds. Attenuation of light is important in physical oceanography. Here, attenuation is the decrease in light intensity with depth due to absorption by water molecules and scattering by suspended particulates. This same effect is an important consideration in weather radar as rain drops absorb a part of the emitted beam that is more or less significant depending on the wavelength used.

 ......ultrasound can also effect transmission in fiber optic lines, which is what ROV's use to send all data to the surface., but I'm sure you read those Wikipedia pages, right ?

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