Following some discussions on waves in water, I feel behoven to wonder whether a piezo device could create ripples with wavelengths approximating that of light (or a few multiples thereof).
If so, the water surface would be tuneably iridescent, which would be pretty.-- MaxwellBuchanan, Apr 21 2012 McTartan_27s_20Chav_20Attracting_20Lake you might like.... version of something similar, but with a purpose! [xenzag, Apr 22 2012] AHA, maybe it is possible... http://phys.org/news110191847.htmlnot from the surface, but from microstructures slightly underneath [4whom, Apr 23 2012] Surface acoustic wave http://en.wikipedia...rface_acoustic_wave [xaviergisz, Apr 23 2012] Acoustic iridescence http://usir.salford...ASMAN12931165_1.pdf [xaviergisz, Apr 23 2012] Capillary waves http://en.m.wikiped...wiki/Capillary_waveBased on surface tension and gravity. [Ling, Apr 23 2012] Iridescent water. http://www.bluefing.../cloud-iridescence/sorry, couldn't hep m'sef [2 fries shy of a happy meal, Apr 24 2012] Soap bubble screen is 'the world's thinnest display' http://www.bbc.co.u...technology-18671061"Viewers may soon be able to watch films on soap bubbles - after researchers developed [...] a display that uses ultrasonic sound waves to alter film's properties and create either a flat or a 3D image." [Wrongfellow, Jul 03 2012] Ultrasonic Flat Panel Display [xaviergisz, Nov 10 2012] Category: vehicle?-- DIYMatt, Apr 22 2012 Well, there are a limited number of categories to select from, so sometimes you have to fudge a little..
For example, there was not a single "weapons: bioweapons:cute" category I could use...-- not_morrison_rm, Apr 22 2012 I think the killer will be viscosity - as wavelength gets smaller, the ratio of kinetic energy to viscosity gets smaller. Once critical damping is reached, there will be no wave propagation at all.
You might be able to get shorter wavelengths on mercury than in water, though, due to its greater surface tension. Short enough? Don't know.-- spidermother, Apr 22 2012 Maybe I'm misreading, but ripples in water won't make it glow. To get visible light you have to knock off some photons, i.e. Cherenkov radiation.-- DIYMatt, Apr 22 2012 //won't make it glow//
Iridescence isn't about generation of light; it's the modulation (amplification/attenuation) of different wavelengths of light, with the result that the color of the reflected light is dependent on the angle of the reflection.-- lurch, Apr 22 2012 Shimmer me timbres.-- 4whom, Apr 22 2012 ^ <Applause>-- spidermother, Apr 22 2012 Category amended.
Yes, I too had doubts about getting enough energy into the water to create really short [water] wavelengths. There's a lot of new surface to create and maintain, so it'll take a bunch of energy, as well as the aforementioned viscosity.
It's easy enough to make ripples with wavelengths of a few hundred microns, though. We're in need of maybe 10µm ripples or smaller (ie, no more than 20 wavelengths of visible light). So, unless the energy requirements go as the cube (or higher) of the frequency, it ought to be energetically doable.-- MaxwellBuchanan, Apr 22 2012 If you deliver me a few pints of good British dark ale I will send you a few drops of iridescent oil to add to the top of your water.-- AusCan531, Apr 22 2012 //deliver me a few pints of good British dark ale// New or used?-- MaxwellBuchanan, Apr 22 2012 If your "used" ale is still dark, I recommend you consult your physician.-- AusCan531, Apr 22 2012 Hmm, perhaps he has King George's disease. That'd certainly explain a lot.-- mouseposture, Apr 22 2012 Vlad the Impaler is suspected to have had porphyria as well. Although I suspect [MB] would prefer a link to British royalty rather than to some foreigner.-- AusCan531, Apr 22 2012 // British royalty rather than to some foreigner// You're joking, right? George *was* a foreigner.-- mouseposture, Apr 22 2012 Vlad III was a total nutter, but he had no fear of sunshine, being fond of taking noontime tea in courtyards surrounded by his impaled victims, and he rode horses everywhere (acute porphyria causes intense lower abdominal pain). He was also reputedly a formidable warrior, said to have personally slain hundreds in battle; the tachycardia and neuropathy associated with porphyria would have made it nigh impossible to fight for protracted periods. In addition, he planned and executed complex extended military campaigns, suggesting an ordered and logical mindset, all cruelty and sociopathic behavior aside. I don't care what Wikipedia says, I don't think Vlad had porphyria.
(In one of those weird HB coincidences, I happen to be reading a book about him right now.)-- Alterother, Apr 22 2012 //Purposeless//
Artists might disagree.-- Wrongfellow, Apr 22 2012 //the required frequency range is that of infrared.//
I don't think that can be correct. We are aiming to create ripples (say) 10µm apart or so.
The frequency of infrared is on the order of a terahertz (10^12 Hz).
Hence, your calculation implies that the ripples are propagating at 10^7m/s.
Which seems unlikely.-- MaxwellBuchanan, Apr 22 2012 I think you're confounding things that should remain unconfounded.
I'm saying that we need to make ripples on water, those ripples having a spacing on the order of 10 microns.
The *wavelength* of these ripples (on the water surface) is roughly similar to the *wavelength* of infrared light.
However, assuming that ripples on water move at less than the speed of light, their *frequency* is of course very much less than the *frequency* of infrared light.-- MaxwellBuchanan, Apr 22 2012 Once again, we're unnecessarily arguing in a vacuum. The few peer-reviewed papers I've been able to find on the subject suggest that the limit is about 70µm, and that much beyond that viscosity does indeed prevent the production of water-air surface waves. Wavelengths of that order are produced with two laser beams detuned by the corresponding frequency. The water is thus subjected to pulses of heat at the beat frequency of the two laser beams, which in the case of 70µm surface waves is about 35kHz.-- spidermother, Apr 22 2012 I've changed the figure to 35 kHz, because I misunderstood the context - on rereading, that paper used up to 100 kHz, but did not get good surface waves at that frequency. A different paper more clearly suggests that 70 µm corresponds with 35 kHz.
I lifted that figure from a couple of research papers. It's the frequency and speed of the surface waves, not of the light.-- spidermother, Apr 22 2012 Well, others used "a piece of a razor blade (1x1cm) soldered down to the 3cm long wire which is pasted to the membrane of the speaker", but were only working with a few hundred Hz.-- spidermother, Apr 22 2012 OK, I can't find any clear statement of the speed of ripples on water (and I presume it depends on their wavelength and on other factors. But, let's guess a propagation speed of 1m/s.
We need a wavelength of (say) 10µm, which equates to an excitation frequency of 100kHz.
Hmm - that is quite high. But you might get some iridescence even at a wavelength of 100µm (they'll just be higher-order reflections - or do I mean lower order), or 10kHz, which sounds reasonable.-- MaxwellBuchanan, Apr 23 2012 Actually, this could fail at being purposeless.
If you could contrive many little ripple-tanks side by side, each independently driven, you could bounce white light off them and have a display.-- MaxwellBuchanan, Apr 23 2012 (GM) bioluminesence?-- normzone, Apr 23 2012 //(GM) bioluminesence?//
Exactly! But without the GM, bio- and luminescence parts.-- MaxwellBuchanan, Apr 23 2012 //surface wave speed and its 'much slower'//
Suggested experiment: take a plastic sandwich box full of water, and tap one side. The ripples definitely take an observable time (>0.1s?) to reach the other side, giving a speed o.t.o.o. 1m/s.
These ripples have a long wavelength (maybe a millimetre or a few), and I'm guessing that shorter capillary waves travel faster, and it's all a bit guessy.
//but with oscillations below the surface you really would need 150MHz// I'm not quite sure what you're saying. (Actually not at all sure.) If you're talking about compression waves ("sound") in the body of the water then, yes, the speed will be high and hence so will the necessary frequency. But compression waves in the body of the water wouldn't do much to light anyway.
But your point does trigger another idea...-- MaxwellBuchanan, Apr 23 2012 La Chance ne favorise pas les esprits mal prepares. [bigsleep] discovered amphibian butterflies, and concluded "nothing happened."-- mouseposture, Apr 23 2012 "Said the mouse of cream yellow birds"?
C'est quoi ce bordel?-- UnaBubba, Apr 24 2012 Bien sûr, vous faire. Comment naïve de moi.-- UnaBubba, Apr 24 2012 Ah, putain! Mon mauvais. L'argot est difficile.-- UnaBubba, Apr 24 2012 Vous n'avez pas à l'avaler, vous le faites?-- UnaBubba, Apr 24 2012 I'l ont deux coups d'argent, monsieur hôtelier.-- UnaBubba, Apr 24 2012 Oh, fantastique! Olympia? Oh, vous avez dit Monet? Olympia était la prostituée, non?-- UnaBubba, Apr 24 2012 L'enlèvement est obligatoire.-- UnaBubba, Apr 24 2012 Bon, bon, jusqu'à demain, mon ami!-- UnaBubba, Apr 24 2012 It's almost 4pm Tuesday. Not exactly sure where you are.-- UnaBubba, Apr 24 2012 I'm sorry, this must be the FrogBakery. I was looking for the HalfBakery. My mistake.-- Alterother, Apr 24 2012 [Wrongfellow] - cool link!!-- MaxwellBuchanan, Jul 03 2012 La DemiBoulangerie, c'est là-bas.-- Phrontistery, Jul 03 2012 you need a liquid with extremely low surface tension, but would water with surfactants do the trick?-- Voice, Nov 10 2012 No, you need a liquid with an extremely *high* surface tension (but a low viscosity).-- spidermother, Nov 10 2012 If it's not possible to create short enough ripples for light, it should at least be possible to do this with far infrared or UHF radio (wavelengths about 0.1mm- 10cm).
In fact, what would happen if I made a huge parabolic reflector out of jelly, and then used a piezo to drive ripples in the surface of the jelly? Would I be able to make a tuneable parabolic receiver?-- MaxwellBuchanan, Nov 10 2012 random, halfbakery