[Closed] Physics: Mirrors and lasers.

Hell yes.

yeah, easily

Possibly.

If the light had a powerful enough electric field it might turn the glass into a plasma, which would then dissipate hence 'burning a hole' in the glass.

Plus, in any case the reflective bit of a mirror is a thin sheet of metal at the back, and you can definitely burn a hole in metal with a laser.

Fair enough. So, could you uprate the mirror to resist these higher power lasers? surely if they reflect all of the light then they would not burn?

As you can probably tell, I am not a physicist!

wavelengths.

Are you designing a defence system against future laser-weapons?

I was actually considering the prospect of a Star Destroyer taking on the Enterprise...

😳

No possibly about it, its something we do frequently. It does depend on the type of mirror, in your bog standard mirror the silver backing will vaporise long before the glass melts. Theres a lot of other variables though, wavelength, power densities, mode and even the modal distribution will effect what happen to the mirror.

Well.. if you could make a perfect mirror then no... as it would reflect all of the energy, and not absorb any.

I suspect that making a perfect mirror might be a bit tricky though!!

Can't you make a near perfect mirror with prisms or something rather than a reflective material

They are using lasers to generate cold fusion. So absolutely yes.

unlikely to be able to uprate the mirror ( as you put it ). at high power, any loss induced in reflecting/reflecting the light would create a warming effect. also any contaminants in the path would do the same, creating localized heating, and it all goes downhill Very quickly from there. 🙂

Can you not get the mirror to reflect Jessica Alba... therefore making it perfect?!

See what I said Torm. Any material can be turned into a plasma.

An atom has a positive nucleus and negative electrons. When you apply an electric field, the electrons get pulled one way and the nucleus the other. If you apply a strong enough field the electrons and nuclei part company, so you have a soup of electrons and nuclei. This soup doesn't have any atomic bonds any more so ends up like a gas.

Light is an electric field and a magnetic field in lots of random chunks in all directions. In a laser, all the chunks are aligned so the electric field can be really strong. The more powerful the laser the stronger the electric field.

If you zap things with lightening, the electric field is very strong indeed and things tend to vapourise. Likewise with a welder.

(note the above may be b*lx, it's been a long time!)

Mmm... Jessica Alba....

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What was the question again?

Clong,
where do you work?

The "perfect" mirror kind of exits. In a traditional ruby laser, a 100% is at one and a 99.9% is at the other, which is how the laser "lases". But its wavelength specific.

Del: I work in the big bad oil industry, i design/build lasers to monitor oil flow using fibre optic.

Cool job!

Lasers and Oil - Do you think they would let me play?

Torminalis - Member
I was actually considering the prospect of a Star Destroyer taking on the Enterprise...

[img] [/img]

[i]Frickin' lasers[/i]

How about if the mirror is underwater?
I'm just wondering about how to protect myself from Sharks with frickin lasers.

Bollocks! 🙂

Torminalis - Member
I was actually considering the prospect of a Star Destroyer taking on the Enterprise...

Ah but which Enterprise .... after all there have bee more than a few
Enterprise NX-01, 22nd century,
USS Enterprise NCC-1701, Constitution class, 23rd century
USS Enterprise NCC-1701-A, Constitution class, 23rd century,
USS Enterprise NCC-1701-B, Excelsior class, late 23rd century,
USS Enterprise NCC-1701-C, Ambassador class, 24th century
USS Enterprise NCC-1701-D, Galaxy class, 24th century,
USS Enterprise NCC-1701-E, Sovereign class, 24th century

plus reference to others in asssorted timelines ......
🙄

</geek mode >

What if the lasers were mounted on a plane on a conveyor belt/

would the backwards thrust of the lasers stop it taking off or would the reflected laser just kill the pilot?

Don't be such a stupid idiot.

What if the lasers were mounted on a plane on a conveyor belt/
would the backwards thrust of the lasers stop it taking off or would the reflected laser just kill the pilot?

Interestingly * using radiation pressure from light to generate thrust is (a) entirely feasible whilst also being (b) the least efficient possible use of energy to do so.

* This may be a matter of opinion

Torminalis - Member
I was actually considering the prospect of a Star Destroyer taking on the Enterprise...

for this reason, i'm reconsidering inviting you to my sexy party.

See what I said Torm. Any material can be turned into a plasma.

An atom has a positive nucleus and negative electrons. When you apply an electric field, the electrons get pulled one way and the nucleus the other. If you apply a strong enough field the electrons and nuclei part company, so you have a soup of electrons and nuclei. This soup doesn't have any atomic bonds any more so ends up like a gas.

Light is an electric field and a magnetic field in lots of random chunks in all directions. In a laser, all the chunks are aligned so the electric field can be really strong. The more powerful the laser the stronger the electric field.

If you zap things with lightening, the electric field is very strong indeed and things tend to vapourise. Likewise with a welder.

(note the above may be b*lx, it's been a long time!)

Molgrips is secretly a nobel prize winning physycist.
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Not..

a nobel prize winning phys[b]y[/b]cist.

Doh physicist.

And toys is a champion speller
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Not

for a good mirror you need a Bragg stack.
very wavelength specific but can get 99.9999% reflective - it's how VCSELs work (a type of semiconductor laser).

my nob is very shiny; but i don't think i want anyone to point a lazer at it?

I was actually considering the prospect of a Star Destroyer taking on the Enterprise...

I am secretly a nobel prize winning bullsh*t artist.

The enterprise latest class is much much faster so could always run away. It is massively outgunned though A star destroyer crew is 30,000 + so it is a no brainer IMHO. The enterprise might win by cunning and repolarising something with an inverse tachion[spell?] beam if the engines could only take it though.
The actual physics PHHHT neither know nor care

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I am secretly a nobel prize winning bullsh*t artist.

Amen to that, it sounded convincing..

I made the mistake of googling this. It would seem that about half the internet is dedicated to this debate! Who'd have thunk it!

Hmmm, maybe I'm thinking too much (or too little) here.

A mirror reflects light.
Laser is light.
If the laser burns the mirror then it was not reflected.
So the mirror was in fact not a mirror.
BUT
Lasers burn things
So if the mirror reflects the laser.
Then the laser wasn't a laser as it didn't burn it.

I need to go to the toilet now.

Mirrors are not perfect tho DrR. That's the thing.

Mirrors are not 'perfect' nor do all lasers burn things. For a laser to burn a mirror you need a mirror with a relatively low reflectivity and a 3W laser.
For those interested, the problem with 'perfect' mirrors is when you build up the mirror layers the individual layers are put under stress causing curving of the mirror face....as i am finding out at the moment!

So I was thinking - can you reflect light with some other kind of field other than a physical sheet of solid?

Perhaps a plasma contained within a flat magnetic field would reflect light?

Pretty sure you can design a matrix of electric field etc to reflect light. For example I think they designed one with a negative reflective index a few years ago?

Edit: [url= http://en.wikipedia.org/wiki/Metamaterial ]linky[/url]

But photons have no charge, so how would they bend in an electric field?

EDIT: Oh the optical properties are refractive.. I see... Still vulnerable to vapourisation tho?

we could build one and find out!

What mirror for moorland riding?

Forget the Enterprise vs Star Destroyer nerdfest...

Fight Club!

Sharks with frikkin' lazors (sic) vs Dolphins equipped with seamines

Who would win? And why?