Naked Science Forum
General Science => General Science => Topic started by: arumalpra on 27/12/2012 06:10:52
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can't we do this? At 6 PM, take rays of sunlight in to fiber optic ring, keep it circulating 2 hours and take out at 8 PM?
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each time the light reflects off the walls of the optic fibre some of the light energy is converted into heat : the light dims as it passes along the light-guide ...
(https://upload.wikimedia.org/wikipedia/commons/thumb/f/f4/TIR_in_PMMA.jpg/320px-TIR_in_PMMA.jpg)
https://en.wikipedia.org/wiki/Total_internal_reflection
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Light storage technology is being pursued by many research groups, as it is one vital component in an all-optical computer.
In normal optical fibre, light travels at about 5μs/km (about 2/3 of the speed of light in a vacuum), and loses power at about 0.2dB/km. This means that 99.9% of the light is lost after 150km, or 750μs. That is not very long-term storage.
In quite exotic optical fibre, losses can be as low as 0.01dB/km, but that only extends storage out to 15ms.
It is possible to slow down light significantly - the current record is 17 meters per second, or 61km/h - you could drive faster than this! http://en.wikipedia.org/wiki/Slow_light
However, currently it only works for narrow bandwidths of light pulses, in rather exotic materials primed by carefully-tuned lasers.
These techniques only give "sequential access" optical storage, similar to the very earliest computers in the 1940s & 1950s. What researchers really want is the equivalent of "random access" optical storage.
Odd: In fiction, "slow glass" was the concept of a window pane that you could place outdoors for years, and then have nice scenery indoors as the images propagated through, over the following few years: http://en.wikipedia.org/wiki/Slow_light#Slow_light_in_fiction
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Evan - wikipedia seems a bit out of date. According to some physicists light can be completely halted!
Liu, c., Dutton, Z., Behroozi, c.H., and Hau, L.Y., Observation of coherent optical information storage in an atomic medium using halted light pulses. Nature 409, 490-493 (2001).
Electromagnetically induced transparency is a quantum interference effect that permits the propagation of light through an otherwise opaque atomic medium; a 'coupling' laser is used to create the interference necessary to allow the transmission of resonant pulses from a 'probe' laser. This technique has been used to slow and spatially compress light pulses by seven orders of magnitude, resulting in their complete localization and containment within an atomic cloud. Here we use electromagnetically induced transparency to bring laser pulses to a complete stop in a magnetically trapped, cold cloud of sodium atoms. Within the spatially localized pulse region, the atoms are in a superposition state determined by the amplitudes and phases of the coupling and probe laser fields. Upon sudden turn-off of the coupling laser, the compressed probe pulse is effectively stopped; coherent information initially contained in the laser fields is 'frozen' in the atomic medium for up to 1 ms. The coupling laser is turned back on at a later time and the probe pulse is regenerated: the stored coherence is read out and transferred back into the radiation field. We present a theoretical model that reveals that the system is self-adjusting to minimize dissipative loss during the 'read' and 'write' operations. We anticipate applications of this phenomenon for quantum information processing.
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can't we do this? At 6 PM, take rays of sunlight in to fiber optic ring, keep it circulating 2 hours and take out at 8 PM?
Typically what happens is that light enters a medium and is absorbed and the re-emitted by the atoms and that's how it propagates through the medium. So whatever photons enter its different photons that remain inside. Only the energy can be stored to date. Of course there is that stopping of light that someone mentioned but I don't know anything about it. Perhaps that's a way to do it and maintain the same photons. Then again it doesn't matter since in principle two photons with the same momentum cannot be distinguished.
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I'm trying to build a solar heater for my swimming pool. Is there a way I can use a dish to concentrate sunlight and funnel the light into an optic fibre, the sunlight would be carried directly into the pool through the optic fibre and heat the water up directly? The reason I'm thinking of this approach is I don't have to heat anything up or generate any electricity to heat the water. The sunlight goes directly into the pool water and heats it up the water. If this can be done, I would think it would be very efficient.
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I'm trying to build a solar heater for my swimming pool.
The surface area of the solar-collector/reflector would have to be comparable with the surface area of the pool, probably bigger, to be of any use.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fimages.h2ofun.co.uk%2Fgraphics%2Fpool-solar-plan.jpg&hash=68fa1dcf2b9bc4d1fa8d6f55bbaf9819)
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For the months over Christmas, many Australians save daylight. I wonder how much we have in the bank now...