if you go in a room of mirrors and turn on a laser the laser light reflects off the mirrors bouncing back and forth eventually filling the room with what seems to be hundreds or thousands of reflections. ok, now turn off the laser, where does the light go? should'nt it keep bouncing around the room of mirrors forever? or at least for sometime after the laser is turned off? light from the stars travels huge distances to our eye,s, it keeps going in 360 deg. from the source forever, so why does the light from a laser in a mirrored room stop or dissapear the instant the laser is turned off?
213370
Ernie... I love this question..  it rocks.\n\nThe answer, however, is going to be just a little dissappointing.\n\nAs I'm sure you know, all light is both a particle and a wave; it is a form of nearly pure energy.  As we know from theoretical physics, energy can never be created, nor can it be destroyed.  It just changes forms.  According to the third law of thermodynamics, energy always goes from higher to lower forms when left on its own, the lowest form of energy often being considered to be heat.  And that's where your wandering, amazing laserlight goes, it turns to heat.  \n\nWhy?\n\nBecause your room of mirrors is completely imperfect.  Your mirrors are dismally inefficient reflectors of light, and the room is full of air.  Household mirrors actually reflect less than 25% of the light energy that shines on them back to you.  Lab quality mirrors made for laser work are, I believe, in the high 80% to low 90% reflectivity efficiency range.  Every time your beam hits a mirror surface and bounces off, it looses more of its energy to heat..  just as it does as it passes thrugh every atom and molicule that makes up the air in the room as well.  Your laser might make it one or two 'miles' of beam length in the room before it is bouncing around.. which would make for thousands of beams.  But, since light travels at 186,000 miles per second, your two mile beam lasts 1/93,000th of a second after you turn the power off before it's gone.  So, it DOES keep going.. but not long enough for you to percieve it.\n\nSo, IF you had perfect mirrors, IN a perfect sphere (remember; you couldn't have any corners!) a COMPLETE vacium inside it with NO particles of dust of ANY kind, and a way to fire the beam into the amazing sphere without leaving any void for energy to escape...  your theory would work, if all that were PERFECT.  But; the biggest catch would be; you could never know if it were working!  Because to find out; you would have to have a void in the sphere to see or measure it...  and measuring any energy source draws energy from it.. so, there goes your light again.\n\nSo, that's why, but it's still a great question.  Theoretical Physics is full of stuff like that...  and thinking about it will turn your brain into silly putty for days.  Keep 'em coming, Ernie..  you've got a great future if you keep your mind working like that.
632800
When two waves of the same wavelength are 180 degrees out of phase, they will destructively interfere with eachother.\n\nWhen the crest of one wave means the trough of another wave (180 degrees, 1/2 cycle, apart), they cancel out.\nYou are left with noting.\n\nhttp://www.glenbrook.k12.il.us/gbssci/phys/Class/light/u12l1b.html
548613
On the contrary, a light beam would merely percieve that it travelled instantly inbetween origin and destination. Space would be warped to Zero distance in the direction of travel, not Zero space. I know it seems like a sleight-of-hand trick with the mathematics, but the distinction is important.
69324
It is Olbers' Paradox.\n\nWhy isn't the night sky as uniformly bright as the surface of the Sun?  If the Universe has infinitely many stars, then it should be.  After all, if you move the Sun twice as far away from us, we will intercept one quarter as many photons, but the Sun will subtend one quarter of the angular area.  So the areal intensity remains constant.  With infinitely many stars, every angular element of the sky should have a star, and the entire heavens should be as bright as the sun.  We should have the impression that we live in the center of a hollow black body whose temperature is about 6000 degrees Celsius.  This is Olbers' paradox.  It can be traced as far back as Kepler in 1610, and was rediscussed by Halley and Cheseaux in the eighteen century; but it was not popularized as a paradox until Olbers took up the issue in the nineteenth century.
185962
There are no materials that are 100% reflective.  Silver and aluminum are in the 90% range, but nothing is 100%.\n\nIf you had a room covered in 95% reflective materials, it would still dim almost instantly after turning off the light.  Light travels about 186,000 miles in one second.  If your room were 10'x10', a light beam about be hitting the walls around 10,000,000 times in the first second, losing 5% of its energy each time.  In the first 1/100,000th of a second, its energy would be reduced to about 0.6% of its orignal value, much faster anyone would notice.
629893
I'm imagining that you're looking into a tube with the other end initially open, and then closing the other side.\n\nInitially, you can see light in the tube because photons are continuously streaming out from light sources, into the tube, and bouncing down towards your eye, all at the speed of light. You can observe this light because the photons are falling on your retina and being absorbed and recorded.\n\nWhen the light source is shut off, the photons currently within the tube -do indeed continue to bounce about the tube-, however, they will all quickly reach the end of thier journey, either absorbed as heat by the tube, or by your retina. \n\nImagine a cop looking for speeding cars on a stretch of highway. There is a traffic accident a few miles up the road, blocking all traffic. For several minutes, though, the officer will continue to observe the cars passing by him. After he has observed all the cars that got through before the accident, there will be no more cars observed until the accident is cleared away. If the cars were moving at the speed of light, the traffic would appear to drop to nothing (in this analogy, darkness) almost immediatley.\n\nThis is analogous to what you're seeing, but the difference is that the photons (usually) don't somehow escape, theier energy is absorbed over many, many collisions and reflections.
126274
You neglect to mention whether the light hits the mirror on its axis of rotation.. assuming that it does, the reflected ray is delfected through twice the nagle that the mirror moves.. thus, 40 degrees.\nLook up "optical lever"
81446
LASER is the acronym for "Light Amplification by Stimulated Emission of Radiation".  It is, first, a process that is explained by quantum mechanics and statistical mechanics.  At this point, it has come into common use, and can also refer to either the light or the device used to produce this type of light.  It does not have a higher energy than light produced by other means, as the energy only depends on the frequency of light.  It does have a higher intensity concentrated into a smaller area, and much higher coherency than light from the sun or a light bulb.\n\nAlso, all light, regardless of how it is produced, travels at approximately 300,000 km/sec in a vacuum.  That value does not differ from one type of light to another, or one color of light to another.
17758
I hope you don't take this to be something of a cop-out answer. Light is itself an electromagnetic field that is carrying energy through space -- commonly called an electromagnetic wave or 'light'. It is this wave that really makes things visible.\n\nConversely, if you have no electromagnetic wave or one of an invisible wavelength, (at least to the human eye) then it won't bounce off of the object or if it does it won't be visible when it reaches you.\n\nThe visible properties of an object are determined by how EM waves interact with the electrons near the surface of an object. These interactions are what make shiny things shiny (for instance).
200723
Actually it's the other way around, the red is what is reflected and most of the rest is absorbed.  It has to do with the different wavelenths being absorbed by different atoms on the surface.  Some atoms or atomic bonds will reflect certain energies and absorb others.\n\nOr they can absorb energy and re-emit it as a lower energy photon which can also happen.
110269
Light gets reflected off mirrors.  If you think of light as a wave the same wave incident on the mirror will come back but at the opposite angle to the normal (that is a line at right angles to the mirror).  That is why you can use mirrors to look at different angles.
86896
No matter how big or small a telescope is, photons of light still have to touch the 'scope mirror in order to be seen and/or photographed.\n\nIt's interesting, though, to realize that with these big telescopes we're seeing extremely distant objects as though we'd been physically transported thousands of light years closer to them. For example, if you're looking through a 20-power telescope at some galaxy that's 10,000 light years away from Earth, the view through the telescope is as if you're only 500 light years away.\n\nGod is spelled B-I-G B-A-N-G\nPBrax@netscape.com
313359
Yes.   Many lasers are pumped with incoherent light.   The first laser ever made was a synthetic ruby cylinder about as big as a pencil with a mirror at one end and a half-silvered mirror at the other.   A xenon tube, like a photographer's flash tube, is wound round the cylinder.   Incoherent light from the xenon tube pumps the laser and a coherent beam of red light emerges from the half-silvered end.
455351
Well, obviously the sun doesn't stop outputting light just because we're cloudy.  We're still getting 1120 W/m^2 through the atmosphere.  It's just being reflected, scattered, or absorbed by clouds, moisture, etc.\n\nSince clouds appear white from space, that says that a big chunk of the sunlight that would otherwise have it the ground winds up sailing off into space.
271509
If there is 10 degrees between them and both strike the mirror at 5 degrees then they will both make the same angle reflecting. !0 degrees between them.\n\nIf one ray strikes the mirror at 0 degrees and reflects straight back, the other will reflect at 10 degrees, same answer.\n\nIf one ray strikes the mirror at 10 degrees then the other ray will strike at 20 degrees. Reflected angles are 10 and 20 so it's still 10 degrees between them.\n\nYou need to subtract instead of add the angles.
1809
you either need more information, or this is a trivial problem. \n\ni am assuming the two surfaces of the glass are parallel to each other, so it's not a prism or lens, but a thin flat plate.\n\ntreating it very simply, you could argue that energy is conserved, so the irradiance (which is energy per second per square meter) must be conserved.  the speed of light is fixed in air, so the "per second" part is fixed too.  if the glass surfaces are not angled with respect to each other, then the light leaves the glass taking up the same area that it went in with.  this means the irradiances are the same.\n\nthis is a simplistic physical model, though.  realistically, you will get some reflection at the air-glass interface, reflection at the glass-air interface, and some absorption (both in the air and in the glass).  you need a lot more details about the problem to say anything meaningful though.
502324
We only see the light reflected off of an object.  Google the invisibility cloak that scientists have comeup with.  It works by refracting and redirecting light .