can a laser beam pass through a reflecting mirror?

Answer 1

Only if it is a cutting laser applied for a long time, and it is not a front surface mirror.

Answer 2

Yes, and no.

It would depend primarily on the type/quality of the mirror and the length of time the laser light was applied. There any many types of mirrors and many types of lasers. An ideal reflecting mirror would reflect 100% of the light (energy) applied to it, no matter the wavelength or length of time, however since such quality is not available in the real world the mirror in question would be absorbing a minute (small) amount of energy due to some light not reflecting (being absorbed).

Over time, this energy would heat the mirror (probably causing its reflectivity to further diminish in the process) until eventually the beam cut a 'pass' through the mirror or slowly heated the mirror until it was a puddle of molten goo. The speed of that process would depend on the power of the laser, the wavelength in comparison to the material of the mirror, the temperature of the mirror, etc.

However, even for a low quality mirror, this would require either a fantastically high powered laser (allowing the 'cutting a pass effect') or a exorbitant amount of time (allowing the melting effect), and for most practical purposes neither would likely be available. For the melting possibility, assuming normal conditions, it is more likely that the mirror would simply radiate the accumulating energy as infra-red (heat) radiation before it ever got hot enough to melt the substance of the mirror.

If you wish to know about mirrors intended for use with lasers (and not just the sort you'd find above the bathroom sink), you may find the following helpful:

From http://en.wikipedia.org/wiki/Mirror#Composition
"Mirrors designed for special applications, such as in lasers and other advanced optical devices, use a reflective optical coating composed of many layers of different dielectric materials. Such coatings can be designed to have extremely high reflectivity and are reasonably durable. Since they absorb very little of the incident light, they can be used with high power lasers without being damaged by the intense beam."
The coatings are on the front surface rather than the back, as stated in the paragraph preceding the quote.

Further down the same article,
http://en.wikipedia.org/wiki/Mirror#Instruments
"For scientific optical work, dielectric mirrors are often used. These are glass (or sometimes other material) substrates on which one or more layers of dielectric material are deposited, to form an optical coating. By careful choice of the type and thickness of the dielectric layers, the range of wavelengths and amount of light reflected from the mirror can be specified. The best mirrors of this type can reflect >99.999% of the light (in a narrow range of wavelengths) which is incident on the mirror. Such mirrors are often used in lasers."

Note 1: You could say (at least for your typical reflective backed glass mirror) that any reflection is the laser passing through the mirror. Semantics, perhaps, but most glass mirrors reflect light off a coating on its back surface and the glass is merely holding the actual reflecting substance in shape. This means the light is passing through the glass of the mirror twice.

Note 2: The 'cutting a pass' effect is essentially high-speed melting. The material with which the laser comes into contact is heated rapidly, vaporizing instead of melting it. This is termed sublimation. You might have heard of sublimation in relation to ski slopes, wherein ice becomes vapor and skips the liquid water phase. If the material melted, it would absorb light differently, and probably block the laser from continuing further.

Note 3: Don't forget about "laser-etched" products, including glass although again, not all mirrors are made of glass. To cut quartz glass, a CO2 laser is needed - http://www.rofin.com/index-fe.htm?start=/english/applications/laser-macro/laser-cutting/glass.php - but then the reflective material coating the 'back' of the mirror may or may not be cut by the same type of laser.


P.S. A bunch of information and links were added to this response 10/06/06. Please re-read if you only read it before that date.

Answer 3

Correct me if I'm wrong here but I thought lasers used reflective mirrors as a means of stimulating the photons and electrons to cause a cascade effect. One of the mirrors is half-silvered usually to allow some light to be reflected. This is the laser light! So I guess the answer is No.

Answer 4

Depends if the laser can gather enough energy to melt the glass and reflective material. I wouldnt stand infront of the mirror when doing a test though. lol

Answer 5

A quadrillion-watt graser beam will pass through the mirror, the wall behind it and whatever planet happens to be in the way.

Answer 6

NO, IT CANT BECAUSE IT IS A REFLECTING MIRROR, THEY USE MIRRORS ALL THE TIME TO GUIDE AND DIFUSE LASER LIGHT

Answer 7

depends on the laser

Answer 8

If it has power enough, it can pass through several feet of steel, so, I think yes.

Answer 9

yes

Answer 10

no u cant coz when u do that it will come back to you!!