Just out of my  curiosity, and with an ulterior motive, but considering how a high power laser would behave if it was to hit a mirror surface.  There are, as far as I know, two possibilities, it would either reflect, and in the process lose te coherence that concentrates the energy.  The other possibility, and here is where I don't have any experience with high power lasers, it might just see it as a surface to burn through.

Anyone have any laser experience to say which would be the most likely?  (Sci-Fi thing, thinking armor against other light weapons surrounding remotely controlled weapons which I have yet to make, not hand held, mounted in defensive structures.)

D.

It will reflect without issue; the coherence is not lost, provided the mirror is flat...

EDIT: Actually, a flat mirror might not be necessary for retention of coherence provided the incoming and outgoing beams don't intersect.  hborre would know...

Lasers are beams of highly collimated, or 'coherent' light.

In real life they're only visible because (a) laser shows generally happen in dark surroundings and (b) the atmosphere scatters some of the light off its path towards the viewer. They normally turn on the smoke machines so the lasers have plenty of tiny particles to get scattered by.

In normal conditions - room light or daylight - in the scenario you describe, you'd see a faint spot on the mirror (scattering by the glass) and another spot on whatever surface the laser is reflected onto; the  beam itself would be somehwere between hard to see and invisible.

All that presumes that it's a visible light laser. A high-energy laser weapon would probably work in the far infra-red, and therefore be invisible to you and me. Whether such a beam would destroy a mirror or not would depend on how reflective the mirror was (or how little of the energy in the beam it absorbed).

The laser weapons you see depicted in Star Wars etc. would almost certainly not look like that if something similar could be developed for real. To get that effect in Poser, you'd need to make a prop (an elongated cylinder) and a shader setup to get that glowing effect.

Mirrors (and prisms) are used all the time to turn or split laser beams. They do not burn through.

In fact, the famous Michelson Morley experiment was all about using beam splitters (half mirrors) to send a single coherent beam in two different directions over some identical distance, send them back, and compare them, as an attempt to detect relative motion wthin the "aether".

The laser stayed so coherent and synchronized that it proved there is no such thing.

http://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment

Actually, the Michelson–Morley experiment predated the invention of the laser by about 75 years. They used white light...

Since you mentioned science-fiction warfare specifically, mirrored armour is considered to be impractical as a defense against weaponized lasers. The fact that lasers use mirrors themselves is irrelevant: the laser being reflected in the vast majority of cases is either low powered (not a weapon), or the mirror is specifically designed for the laser.

In a combat situation a sufficiently powerful laser hitting a mirror will reflect but some energy will remain causing thermal shock which will fracture the mirror. This will also happen if there's some kind of imperfection in the mirror (like dirt) which will allow the energy to be absorbed rather than reflected.

In any kind of ground environment hoping to keep your mirrored armour pristine is, well, as a former soldier, just let me say good luck with that. And that doesn't even consider the possibility that the enemy will actively seek to degrade the mirrored armour's effectiveness.

"Sir, the enemy has deployed a secret weapon that makes our armour vulnerable to their lasers!"

"What kind of high-tech dasterdly device is it?"

"Vacuum cleaners set to reverse so they blow dust out!"

"Damn! How can we defeat such brilliant foes?"

My Sister happened to send me a video about mirrors; it turns out that mirrors tend to be very pale green...

http://www.youtube.com/watch?v=-yrZpTHBEss

I'm not sure if this is due to the coating or the glass; the video doesn't explain...

Quote - Actually, the Michelson–Morley experiment predated the invention of the laser by about 75 years. They used white light...

Ugh - boy I got that story mixed up.

Sorry. I blame 2 hours sleep last night?

Quote - Optical tests of the isotropy of the speed of light became commonplace. New technologies, including the use of lasers and masers, have significantly improved measurement precision.

Yeah - in the 60's or later, right? Duh.

I sympathize BB.  Four hours myself, ergo a stupid question to begin with.  One look into "Amateur Telescope Making", while old is filled with good numbers, including the reflectivity of the different common mirror platings.  Duh!  What isn't reflected is the amount that is absorbed, Oh, well.  Headbone some other kind of defensive armour.

Color of mirror:  If you look at thick plate glass edge on, you see a green color.  This would affect a second surface mirror, but not a first surface.  First surface, each coating has it's own band of strongest reflection, the reflective coating would determine what the color would be.  What is overcoated on a first surface mirror has different purposes, including reflectivity.

D.

Offensive and defensive technology tends to follow each other closely so there is nothing to say your mirror armour has to deflect all the energy to be effective, just enough so the surface and some fancy futuristic super conducting material underneath can vent the remaining heat energy else where. 

(if someone could invent a 100% reflective surface without impurities they most likely could also design it to reflect the laser back to the firer making the attacking weapon unsafe so possibly there is another reason why you wouldn't find lasers and mirrored armour on a future battlefield)

There's also the possibility of using Metamaterials as defensive armour.  The current interest for military applications is giving an opaque surface a ridiculous refractive index and therefore making it invisible.  Far as I understand it, the theory behind Metamaterials is every substance, including completely opaques like concrete, have a refractive index; a Metamaterial coating can be made to alter this to anything at all.

So, maybe a perfect mirror surface isn't beyond the realms of possibility but the way it'd be created would be totally different from the way we'd expect. 

Then again, I could have it totally bass ackwards and be barking up the wrong tree. :)

I seem to remember research into combatting laser rangefinders by the target emmitting a light-dispersing aerosol to scatter the laser. Not sure if you could emit enough, quickly enough to combat weapons-grade lasers

The weapons grade Lazers of today get very very hot.

Would burn,melt the mirror in a few seconds.