What happens if you see a mirror through infrared (night vision) in the darkness?

Question

anyone want to help me with this little homework?

i dont have a night vision camera

thanks!

Answer 1

The initial answers don't really consider the proper information. There are some materials that reflect visible light but are opaque or transparent to others.

Infrared is not "just light" in the same way that microwaves and x-rays are not "just light". They are all controlled by the same thing, photons, but a change from one to the other can be drastically different. Our skin is opaque to our eyes but mostly transparent to x-rays. Many materials are transparent to microwaves, but water isn't so we can use it to cook food that has water in it or water added (meaning a microwave would not be very effective at heating dehydrated food that didn't have water added).

A typical mirror is, in fact, most likely going to reflect infrared light.

However, even if the mirror material didn't, most mirrors are covered with glass, and glass reflects infrared light. That is actually the principle behind how greenhouses work and a reason why cars get so much hotter than the outside (another is reduced convection).

I imagine the principle you are supposed to realize is that the glass actually would reflect infrared light before the "mirror" backing had a chance.

Otherwise, you would have to actually research what mirrors are usually made of and see what kinds of light they reflect. I don't imagine that is your task (though maybe it is).

So you would see a reflected scene. It probably wouldn't be as accurate as the scene you see without the goggles because the glass isn't necessarily as good at reflecting as the polished metal behind it.

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As a side note, infrared goggles are usually called "heat vision" or "thermal vision" as heat results in infrared light. Goggles that are called "night vision" when they act to amplify available light to visible levels. These kinds of "image intensifiers" magnify visible light and sometimes light beyond the human visible spectrum. They usually would stop before the infrared spectrum though.

Image intensifiers allow one to see well in, for example, an empty field on a dark night by amplifying the faint starlight. Infrared goggles would make it harder to see long blades of grass apart from each other (as they are around the same temperature), but someone hiding in the thick grass would stand out like a lightbulb.

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From source:

"The amplification without the IR is typical of 1st Generation (you can see, but in most cases, it's worth it to light up the night w/ your beam). With the IR, amplification is very good, just don't look into any mirrors or glass surfaces (the beam's reflection can be blinding)."

Answer 2

The mirror will reflect infrared as it reflects light, so you will see the reflected scene as if you were seeing it directly through the infrared device.

Answer 3

Infrared light is still LIGHT.

It just isn't detectable to the (unaided) human eye.

Answer 4

Infrared by its nature of wavelength will be reflected in great part by the reflection of the glass, then the silver dioxide at the back of the glass (mirror part), but part of the infrared waves will cross directly the glass and the silver dioxide.

Please, lets not confuse infrared with heat.  Heat produces lots of infrared waves, but infrared does not produce heat in the same quantities.

Most of the part of the Infrared that is reflected by the glass is carrying heat energy (electromagnetic vibration of matter), most of the waves that cross the glass and the silver dioxide contains less heat, and can be considered almost pure infrared.

There are some manufactured filters that reflect head but not bare light used in old film projectors, so the heat from the lamp does not hit and damage the film.  

In some way, heat is also infra-red but with an electromagnetic energy with longest wavelength.  Thus, is easy to produce filters to separate them.