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Why can't I reflect light infinitely? (Read 1781 times)
Nov 2nd, 2011 at 11:00pm

Webb   Offline
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I put a LED night light in the bathroom so I don't have to turn the light on every time I go in there.

I have noticed that the light reflects in the mirror so I can see 2 night lights.

Hmmm, why can't I put mirrors on every wall (other than it would look like a whorehouse) and reflect the light over and over and over again infinitely?

Something tells me there is a basic law of physics that would prevent this - something like laws against perpetual motion.

So college kids (I rank this a little above high school physics and I hope I'm right because I don't remember learning it in high school) - why can't I put mirrors all over the walls and ceiling and magnify a 3w night light into 300 watts?
 

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Reply #1 - Nov 3rd, 2011 at 4:40am

Xpand   Offline
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There isn't any law that stops you from doing that except for the decay of the light intensity at the square of the distance it travels. So, if you had a very intense light you could light up the room, IF the mirrors you had could scatter the light, otherwise you'd have a laser beam that wouldn't light up anything.
« Last Edit: Nov 3rd, 2011 at 8:51am by Xpand »  

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Reply #2 - Nov 3rd, 2011 at 3:39pm

ozzy72   Offline
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Photons get tired Grin
 

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Reply #3 - Nov 3rd, 2011 at 4:38pm

Steve M   Offline
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I think you would need some super magnets like the Large Hadron Collider has. Acme supply has marketed such magnets.  Smiley Another thought crosses my mind, as soon as you enter the room that has the source of light you might disrupt the refraction of light and the house might go dark.


Smiley  ...


  ...


 

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Reply #4 - Nov 3rd, 2011 at 5:41pm

Bud Greene   Offline
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Webb wrote on Nov 2nd, 2011 at 11:00pm:
Hmmm, why can't I put mirrors on every wall (other than it would look like a whorehouse)...

I fail to see the problem here... Wink Grin
 
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Reply #5 - Nov 3rd, 2011 at 5:46pm

patchz   Offline
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Bud Greene wrote on Nov 3rd, 2011 at 5:41pm:
Webb wrote on Nov 2nd, 2011 at 11:00pm:
Hmmm, why can't I put mirrors on every wall (other than it would look like a whorehouse)...

I fail to see the problem here... Wink Grin

Grin Grin Grin Grin Grin

Best reply!!!!!
 

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Reply #6 - Nov 3rd, 2011 at 6:47pm

Ang2dogs   Offline
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patchz wrote on Nov 3rd, 2011 at 5:46pm:
Bud Greene wrote on Nov 3rd, 2011 at 5:41pm:
Webb wrote on Nov 2nd, 2011 at 11:00pm:
Hmmm, why can't I put mirrors on every wall (other than it would look like a whorehouse)...

I fail to see the problem here... Wink Grin

Grin Grin Grin Grin Grin

Best reply!!!!!


This is why I make sure to swallow what I'm drinking before I open a thread, cause you never know what's going to make you bust a gut!  Grin Grin Grin
 
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Reply #7 - Nov 3rd, 2011 at 7:44pm

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This has been a very funny thread so far! Grin

But on a serious note, please keep in mind that I'm not a physicist or expert in anything, especially light reflection. BUT, it seems to me that that wouldn't work, because it does not increase the AMOUNT of light, it just redirects it. for example, if you put a mirror on the wall opposite of the LED, then instead some of the light reflecting from the wall (allowing you to see it) and some of it being absorbed by the wall, all of it is reflected and simply redirected to another area where some of it will be reflected and some will be absorbed. It doesn't matter how much you bounce it around, you only have so much light to work with.
 

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Reply #8 - Nov 3rd, 2011 at 8:00pm

Xpand   Offline
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That's because, in order to iluminate large surfaces you have to diffuse the light using a non-flat surface, like white fabric from shirts.
The only way you could illuminate a whole room with only a source of light is by using the an intense source of light and place it at the center of the room. Then cover the walls in pure white paint with with a cement like rugosity in order to scatter the light.
...
you see the paralel incident rays (blue) and the green reflected rays not paralel. That's the secret of diffusion and it allows you to illuminate large surface areas from a smaller light source.
 

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Reply #9 - Nov 3rd, 2011 at 8:11pm

Steve M   Offline
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Roll Eyes I'll give this one more shot before I have to turn the lights out. And it agrees with Xpand and Tacit. The only way that light could amplify is with polished convex mirrors directed at each other but still using a source of radiation. Basically a laser, in a whorehouse of course.  Grin
 

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Reply #10 - Nov 3rd, 2011 at 10:35pm

Webb   Offline
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What a hoot.  I'll have to see if I can come up with more stupid questions (involving whorehouses of course).
 

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Reply #11 - Nov 4th, 2011 at 3:54pm

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Inverse square rule... Mythbusters tested an alternative way of maximum diffusion using mirrors to light an otherwise pitch black room, but it's very hard.

If you double the distance of the light, it quarters its intensity. Incidently, we calculated in physics that you could read your newspaper on Pluto - Because despite the inverse square rule, there is enough light there to be equivalent to being 50cm from a 60W bulb. So now you know!  Tongue
 

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Reply #12 - Nov 4th, 2011 at 7:43pm

Jayhawk Jake   Offline
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I'm willing to bet it also has to do with reflectivity, as in a mirror does not reflect 100% of the light that shines on it.  It's probably close to 100%, but anything off and after a while it will dissipate
 

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Reply #13 - Nov 4th, 2011 at 10:03pm

machineman9   Offline
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Jayhawk Jake wrote on Nov 4th, 2011 at 7:43pm:
I'm willing to bet it also has to do with reflectivity, as in a mirror does not reflect 100% of the light that shines on it.  It's probably close to 100%, but anything off and after a while it will dissipate

About 85-90% for a typical aluminium mirror. Some light will be absorbed as heat, some light will be diffused, some will probably be refracted or lost by not being withheld by total internal refraction.

It's not a bad idea to have mirrors everywhere, but I imagine white walls would be more effective and not as painful to look at. (Not saying they aren't boring though  Tongue)
 

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Reply #14 - Nov 4th, 2011 at 10:55pm

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Oh boy, I'm a science junkie here! Grin
Time to have som e fun explaining my theories in the morninig! Grin
Ya know.... Along with that, maybe I should post some of my random theories that may prove current ones wrong.  (I've got some good facts to back em' up too amazingly) Roll Eyes
Let's say, if I do, prepare for a mirage of theories on why the sky is blue, vacuum, fire, energy, E=mc2, and I'll have to dig through my binder to find what else. Cheesy

I'm insane...  I know..........          But it's fun. Cheesy Grin Cheesy Grin Cheesy
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Reply #15 - Nov 5th, 2011 at 12:03am

hyperpep111   Offline
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Hmmm. have you ever tried putting a torch on at night?(Dumb question) You'll see that you can't see miles ahead. You'll only see a few feet in front at most. Same thing. Light loses density after a distance. Which is why if you drive away from a light. Let's say in the middle of a desert. It will appear to get brighter and then get dimmer because light has a greater density than air. Smiley.

Club? WTH? Cheesy
 

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Reply #16 - Nov 5th, 2011 at 12:32am

Webb   Offline
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hyperpep111 wrote on Nov 5th, 2011 at 12:03am:
Light loses density after a distance ... because light has a greater density than air.

I think we have a winner!
 

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Reply #17 - Nov 5th, 2011 at 9:50am

jetprop   Offline
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my reasoning tels me that that is wrong.
air is denser then light.
because light doesn't exert presure(?) and air does.
so technicly light doesn't have ANY density.
but then you also have E=mc squared...

my reason is:
light is energy but also a form of 'matter'.
so when light travels it loses energy.
the more energy,the brighter the light+the more energy the light has.

this is what i think so...

oh btw:
club;
The blue color of the sky is due to Rayleigh scattering. As light moves through the atmosphere, most of the longer wavelengths pass straight through. Little of the red, orange and yellow light is affected by the air.

However, much of the shorter wavelength light is absorbed by the gas molecules. The absorbed blue light is then radiated in different directions. It gets scattered all around the sky. Whichever direction you look, some of this scattered blue light reaches you. Since you see the blue light from everywhere overhead, the sky looks blue.

copy and paste of a teaching website. Grin
 

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Reply #18 - Nov 5th, 2011 at 10:17am

alrot   Offline
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Even in the empty chamber  and using a laser beam,and using crystals (prism)100 pure  that doesn't happen , Your question has my head spinning since you posted  Undecided

 

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Reply #19 - Nov 5th, 2011 at 10:18am

Xpand   Offline
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Oh god... Light doesn't have density, density is a characteristic of objects with mass and volume, neither of which light has... Light has intensity! The intensity of light changes folowing an aritmentic function that decreases with the square of the distance light travels. If you have a light source at x meters from you and another at 2x meters from you the second one will appear to have 1/4 of the intensity of the first. That's why, considering full reflective mirrors, you can't reflect light ad infinitum. Also the ammount of photons is what gives the intensity of light.
Light does NOT have mass but it has momentum, that's why it can eject electrons from atoms or make them change their energy level.

Sorry, I'm a little frustrated!  Shocked

Also, let me correct myself, you can reflect light infinitely, but in the end you'll only have one photon, which you cannot see, because photons loose their momentum, therefore reducing the light's intensity.
 

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Reply #20 - Nov 5th, 2011 at 10:41am

alrot   Offline
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Undecided Quote:
but in the end you'll only have one photon,


remember photon decays when we see it ,light in this case has to be seeing as a wave and not a particle in other words "we put it when we see it" as far I know Light or this part of the electromagnetic radiation spectrum and has Infinitive range in the vacum space otherwise we couldn't see pulsars or Novas in the deep space


imagine  vacuum chamber, and not using a mirrow (Nitrate of plane ,aluminum can filtrate certain longitudes of waves of visible light) the same problems some telescopes carry
We will place Place a perfect and 100% pure Prism

http://www.tcmtoys.com/product_images/g/179/Light_Crystal_Prism_smaller__37828_z...

we will bounce a laser beam , as soon we turn it off ,Its all of
I think this has to be more with the relativity laws

I guess  Undecided
 

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Reply #21 - Nov 5th, 2011 at 10:58am

Xpand   Offline
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The matematical function that describes the light's intesity decay tends to zero when the distance tends to infinity. So, you'd actually end up with zero photons if you reflected light endlessly. The photons are the unit of measure for light intensity. They carry light, just as gravitons carry gravity and give it its intensity. Actually, in order to exist light you must have carrying entities on an electromagnetic field, just like the gravitational field. Those particles can be theoretical, like the gravitons and Higgs or real like protons, since it's proven that light has a particle behaviour as well as the wave behaviour:
Quote:
Light, which is emitted and absorbed in tiny "packets" called photons, exhibits properties of both waves and particles. This property is referred to as the wave–particle duality. The study of light, known as optics, is an important research area in modern physics.


In fact the night vision goggles work by increasing the ammount of photons using a multiplier of sorts...

But take into account that Novas and galactic sized entities have a greater light intensity than the sun alone, therefore they decay less for the same distance. For example the max distance you can see a candle in a black night is about 2 km. If you putted the same ammount of light a galaxy has at that distance you would be blinded even with your eyes closed.

Of course, I'm trying to avoind going into quantum physics here, or else this would be MUCH more complicated...  Grin
 

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Reply #22 - Nov 5th, 2011 at 11:25am

alrot   Offline
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Quote:
you would be blinded even with your eyes closed.


or evaporated  Grin

you got a good point there xpand ..

  Quite of crazy huh? billions of dollars for the LHC and looks like Higgs was wrong  Shocked 

Like this LIGO after a decade no a single wave hasn't been detected yet

Sometimes I think this world is so crazy (especially the weird and strange quantum irrational mechanics ) that we are part of some sort of collective dream ,Like Matrix Movie  Grin

just joking
 

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Reply #23 - Nov 5th, 2011 at 12:09pm

Xpand   Offline
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Well, the LHC already made some important discoveries. If the Higgs is wrong then that doesn't mean the research was done in vain, it just means we have to search elsewhere for the missing piece.
I kinda like to think that the Universe is like a broken pocket clock with all the infinite pieces laying around and we humans as the person who's trying to put the pieces back together so we can make use of that clock to live a brighter future. Most people think we are in the edge of knowledge but I strongly believe science was advancing more rapidly in the 18 hundreds than in the XXI century. I sure hope things make a twist turn and science and knowledge for the sake of mankind instead of war can have a new bright age.
 

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Reply #24 - Nov 5th, 2011 at 12:26pm

jetprop   Offline
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ok we now know the answer:

no
because:
light decreases intensity/loses energy(thats how i say it)
incase you disagree with me:
photons are particals and a partical is matter.
light doesn't have mass but it is matter.
see it as a visible 'dark matter'

mirrors can't reflect all the light.


do we agree?
 

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Reply #25 - Nov 5th, 2011 at 12:47pm

Xpand   Offline
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jetprop wrote on Nov 5th, 2011 at 12:26pm:
ok we now know the answer:

no
because:
light decreases intensity/loses energy(thats how i say it)
incase you disagree with me:
photons are particals and a partical is matter.
light doesn't have mass but it is matter.
see it as a visible 'dark matter'

mirrors can't reflect all the light.


do we agree?


No to all that's in Bold.
Particles are not matter. Matter is particles with mass (atoms).
Photons don't have mass, they are just particles.
Light is NOT matter, you can't grab light with your hand or any other tactile instrument.
Dark matter is not light. Dark matter is a diferent type of matter which is transparent to all types of radiation.
Flat mirrors reflect 90-99% of the light that hits them.

And actually the answer is YES you can reflect light endlessly, but you will stop seeing it after a certain number of reflections, but that doesn't mean there's no light, just like a 10Hz sound is inaudible, but still exists.
 

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Reply #26 - Nov 5th, 2011 at 12:59pm

jetprop   Offline
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Xpand wrote on Nov 5th, 2011 at 12:47pm:
jetprop wrote on Nov 5th, 2011 at 12:26pm:
ok we now know the answer:
no
because:
light decreases intensity/loses energy(thats how i say it)
incase you disagree with me:
photons are particals and a partical is matter.
light doesn't have mass but it is matter.
see it as a visible 'dark matter'

mirrors can't reflect all the light.


do we agree?


No to all that's in Bold.
Particles are not matter. Matter is particles with mass.
Photons don't have mass, they are just particles.
Light is NOT matter, you can't grab light with your hand or any other tactile instrument.
Dark matter is not light. Dark matter is a diferent type of matter which is transparent to all types of radiation.
Flat mirrors reflect 90-99% of the light that hits them.

And actually the answer is YES you can reflect light endlessly, but you will stop seeing it after a certain number of reflections, but that doesn't mean there's no light, just like a 10Hz sound is inaudible, but still exists.



Quote:
Matter is a general term for the substance of which all physical objects consist.Typically, matter includes atoms and other particles which have mass. A common way of defining matter is as anything that has mass and occupies volume.However, different fields use the term in different and sometimes incompatible ways; there is no single agreed scientific meaning of the word "matter".


but this is an impossible to answer question onless we know if photons have mass wich we DON'T.

+if mirrors reflect 99% of the light it would finaly disapear so...
and light can't travel endlessly,otherwise we would be able to see ALL the stars,wich we AGAIN,don't.
 

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Reply #27 - Nov 5th, 2011 at 1:15pm

Xpand   Offline
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Photons have no rest mass. It's mathematically proven.

http://www.desy.de/user/projects/Physics/ParticleAndNuclear/photon_mass.html

And that quote confirms what I've said up there.
Light is not matter. Matter has to occupy a volume and light does not do such thing.
 

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Reply #28 - Nov 5th, 2011 at 2:01pm

jetprop   Offline
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sigh,we all have different oppinions but lets just say that its impossible since mirrors don't reflect EVERY light particle.
most,but not all.
 

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Reply #29 - Nov 5th, 2011 at 3:13pm

hyperpep111   Offline
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I actually said that as a joke. Guess nobody got it  Embarrassed
 

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Reply #30 - Nov 5th, 2011 at 3:31pm

Xpand   Offline
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Eheh, sarcasm, irony or any other implicit joking mark is very hard to detect in the internet. You should have pointed us towards that, lol. Nonetheless it sparked an interesting discussion..
 

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Reply #31 - Dec 11th, 2011 at 12:03am

Webb   Offline
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I got several of these LED lights at the Dollar Store and so far only one has burned out.

But it won't die!

I left it plugged in and over several weeks it keeps coming back on.  Sometimes it's a very dim light but now it's back to its original intensity.

Odd little buggers.
 

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