Physics of light anyone?

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hippie_nz
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Physics of light anyone?

Postby hippie_nz » Sat Oct 27, 2007 11:09 pm

Does anybody out there have a good understanding of the physics of light and could answer a few questions for me about an art project I plan to make??? Any help would be much appreciated.
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Postby Toolmaker » Sat Oct 27, 2007 11:25 pm

Yes.
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Postby Ugly Dougly » Sun Oct 28, 2007 9:38 am

What do you gots?
Particles or waves?

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Postby theCryptofishist » Sun Oct 28, 2007 10:15 am

Me, I gots waves. Cause I'm a fish.
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Postby BitterDan » Sun Oct 28, 2007 11:18 am

Well, what's the question?
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Postby mdmf007 » Sun Oct 28, 2007 12:00 pm

Particles and waves are myfavorite.

drop your questions I am sure we can answer them or point you in the right direction - and throw some banter and subterfuge in as well.

later

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Postby theCryptofishist » Sun Oct 28, 2007 12:29 pm

And we gotta gratuitously include special relativity and schrodinger's cat as well.
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Postby spectabillis » Sun Oct 28, 2007 4:35 pm

not a lot of info to go on, but you sure you need an understanding of physics to figure it out? some club type lighting and fog effects? laser splitting through prisims?

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Postby Dork » Sun Oct 28, 2007 4:49 pm

Please tell me it's a holodeck!

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Re: Physics of light anyone?

Postby stargeezer » Sun Oct 28, 2007 5:35 pm

hippie_nz wrote:Does anybody out there have a good understanding of the physics of light and could answer a few questions for me about an art project I plan to make??? Any help would be much appreciated.


If you provide more information, I would expect you will get a lot of help. Without information, humor takes over and imaginations run wild. Don't let the early responses discourage, if you ask a more specific question, you will probably receive the answers you are looking for.
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Postby hippie_nz » Sun Oct 28, 2007 7:41 pm

well seeming someone may be able to help me heres the question:

I want to make a bright beam of light going into the sky that will fade out to have the focal length of the light beyond the length of the visible light and like this / \ rather then this \ / so the light would look like a triangle with the top point being way up in the air. I'm wondering if this is possible and if someone could explain to me what type of mirrors I could use or explain how I can work out which size and curvature of mirror to use. I'm presuming it is possible as this is what most flash lights use with a concave mirror but it has a very small focal length so the light just crosses not far from the source of light. Any takers? hope that all makes scence.
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Postby Tiahaar » Sun Oct 28, 2007 10:33 pm

OK I'll bite. How large of diameter do you want the base of the cone of light to be, and how high to the tip? If a big base (20-30+ ft?), I'd suggest a circle of pinspots pointing towards the same tip point...you'd get a bright lower cone and a dimmer inverted cone above, no real way to cancel that out, unless say there were a big black light absorbing helium balloon tethered at that location perhaps ?

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Postby Ugly Dougly » Mon Oct 29, 2007 10:13 am

How much money you have to spend on lasers?

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Postby Teo del Fuego » Mon Oct 29, 2007 10:55 am

theCryptofishist wrote:schrodinger's cat as well.


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Postby capjbadger » Mon Oct 29, 2007 5:35 pm

Tiahaar wrote:OK I'll bite. How large of diameter do you want the base of the cone of light to be, and how high to the tip? If a big base (20-30+ ft?), I'd suggest a circle of pinspots pointing towards the same tip point...you'd get a bright lower cone and a dimmer inverted cone above, no real way to cancel that out, unless say there were a big black light absorbing helium balloon tethered at that location perhaps ?


Good luck keeping that balloon at the focal point with the winds out there though. ;)

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Postby BitterDan » Mon Oct 29, 2007 5:52 pm

Depending on the scale and size of the base I would go with either a series of lasers aimed so that the point where the beams cross is higher than a human could visibly see the light or I would go with some high intensity light aimed into a concave mirror (why go through the trouble for that though? just rent a spotlight). You could do the former with only a handful of lasers and splitters arranged in a circular/conical pattern.

Sorry it's not more mathematic/physical but that's what I came up... ON WEED!
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Postby hippie_nz » Mon Oct 29, 2007 6:50 pm

The base of the cone of light will only be about 1-2 ft with the tip being as far as 300-500 ft up, I'm basically trying to create the effect of light shining down from the "heavens above" so that it appears somewhat that the light is being shined from the sky downwards rather then the ground upwards. With the spot lights I've tried so far the light always opens outwards rather then pointing inwards to a point.

I don't have bugger all money for lasers and I want the light to be white anyway, so I was thinking bright lights shined into a concave mirror (most likely very bright LED lights as I will be running it off a battery), but I don't know what curvature I would need it to be and how big it would need to be to create the desired effect.

Hiring a spot light isn't really an option because the light is going to be built into an art project.
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Postby oneeyeddick » Mon Oct 29, 2007 7:36 pm

Nope...That'll never work........Nope, nope, nope !!

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Postby Zulegoona » Mon Oct 29, 2007 8:46 pm

Fresnel lenses can be engineered to have focal lengths of 20 miles as done with light house lights
Image
Image
Image

But it would be incredibly expensive to have an optics engineer design a lens and have the prisms ground and mounted, and then the base of the cone would only be as big as the lens.

The other option would be to use multiple lights aimed to form your cone but the light wouldn’t stop at that target point and there would be an inverted cone above.

Image

Ok so I just went back and read Hippies last post and this isn’t relevant at all but interesting stuff

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Postby mdmf007 » Mon Oct 29, 2007 9:51 pm

No matter what though - your light once it hits the focal point is still going to continue on. Making a one ended cone rather hard to accomplish. if not impossible unless the beams terminate on something. which is not practical.

spotlights aimed at a focal point very high though wold be more effective. The air at altitude above the playa is much cleaner so maybe it would appear to dissapate wuicker leaving a cone.

its pricey to experiment with but playing with the gear would be the easiest way to figure it out.

later

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Postby mdmf007 » Mon Oct 29, 2007 9:54 pm

hmm a lighthouse on playa?

sounds like fun

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Postby stargeezer » Tue Oct 30, 2007 4:38 pm

As stated in other posts, the light will continue upward and give you a second inverted cone if projected from the ground. The only way I can see making something that will match your requirements is to elevate the light source to your focal point and shine the light down. If you use a helium balloon with guide lines, you could send power up one of the guide wires to minimize the amount of weight you need to support. While this would have trouble with wind, during calm times it should work great. You would want enough lift in the balloon to keep the guide lines tight, but balance that by not making it too large to minimize the wind impact. Finally, as a safety note, if something should happen to the balloon, dropping an object from 200-300 feet could cause some significant damage. Surrounding it with soft bulky material such as bubble wrap would keep the downward velocity low and reduce impact energy in the event of an accident.
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Postby oneeyeddick » Tue Oct 30, 2007 4:44 pm

Helium doesn't have enough lift for that kinda weight.
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Postby BitterDan » Tue Oct 30, 2007 5:43 pm

How about hydrogen? At the very least we could witness the fire ball in the sky.
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Postby stargeezer » Tue Oct 30, 2007 8:17 pm

oneeyeddick wrote:Helium doesn't have enough lift for that kinda weight.
Nope...That'll never work........Nope, nope, nope !!


Please tell that to the Goodyear Blimp.

Yes, you do no want a balloon the size of the Blimp, but if you send your power up the guides, make them as light as possible, and minimize the weight of your light, then it is indeed possible. A ten foot diameter balloon could lift about 13 pounds, more weight just requires a bigger balloon.
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Postby S » Thu Nov 01, 2007 2:13 am

... but we do want a balloon the size of a blimp filled with H.

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Postby Ugly Dougly » Thu Nov 01, 2007 9:54 am

Just one laser and a complex set of mirrors.

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Postby oneeyeddick » Thu Nov 01, 2007 5:48 pm

The Goodyear blimp would fail at Burning Man. Too much wind. Air is too thin and warm for helium to have its properties exploited properly.
Nope... That'll never work....nope,nope,nope !!

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Postby stargeezer » Thu Nov 01, 2007 8:45 pm

First off, if you look back through this thread I mentioned that a balloon would have to be used only when wind was not a problem.

Regarding the use of helium at altitude, have you ever heard of something called a weather balloon. It takes a reasonable sized payload way up in the atmosphere to assist in monitoring weather conditions. Now let me see, where does it get lift from??? Now I remember, it is something called helium.

Just as a final reference, hot air balloons operate at altitudes much higher than BRC. Hot air does not provide anywhere near the lift that helium provides, a manned helium balloon has gone higer than 100,000 feet.
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Postby oneeyeddick » Fri Nov 02, 2007 10:07 am

[quote="stargeezer"]First off, if you look back through this thread I mentioned that a balloon would have to be used only when wind was not a problem.

>>>He is gonna be using this at night , right ? Hmmm.... Wind at night at BRC ? Never heard of that.Shouldn't be a prob.......


Regarding the use of helium at altitude, have you ever heard of something called a weather balloon. It takes a reasonable sized payload way up in the atmosphere to assist in monitoring weather conditions. Now let me see, where does it get lift from??? Now I remember, it is something called helium.

>>>>Weather balloons don't have guy wires or 8 to 12 lbs of two strand wire attached to them. The equipt they are toting weighs an average of 3 1/2 lbs.

Just as a final reference, hot air balloons operate at altitudes much higher than BRC. Hot air does not provide anywhere near the lift that helium provides, a manned helium balloon has gone higer than 100,000 feet.

>>>>Well there you go then, just call NASA, and ask them for specs on how to do this. Oops, hold on, he said something about not having a bugger of money for lasers (and such).He would be better off contacting Big Puffy Yellow or the dept of tethered aviation and asking for cooperation with thier time tested techniques.

and, with that said........
Nope... That'll never work....nope,nope,nope !!


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