Darkvision and mirrors?

[Nail]

That was because the drow's ability to see in darkness at the time the novel was written resulted from the ability to see patterns of heat - infravision, not darkvision.

-Hyp.

Strange.

Since infravision sees heat, and heat is a form of light, a mirror would show a heat image to those with infravision.

After all, aluminum foil is useful not because it reflects visible light, but that it reflects other wavelengths as well......

 

[Hypersmurf]

Since infravision sees heat, and heat is a form of light, a mirror would show a heat image to those with infravision.

How well does a piece of silvered glass reflect heat compared to light, though?

If I sit a mirror near a fire, the mirror gets warm... so it's absorbing and transmitting heat as well as reflecting it, no?

-Hyp.

 

[darthkilmor]

Yes a mirror reflects darkvision, because mirrors are mystical portals to a plane of mirrors and do not concern themselves with photons and wavelengths and reflect stuff because....the faq says so? <waves hands> Don't try to explain it with real world physics, just say "Its dark. You are eaten by a grue" and be done with it.

( Mirror Plane ) edit: thanks Ilium!

 

[Ilium]

Yes a mirror reflects darkvision, because mirrors are mystical portals to a plane of mirrors and do not concern themselves with photons and wavelengths and reflect stuff because....the faq says so? <waves hands> Don't try to explain it with real world physics, just say "Its dark. You are eaten by a grue" and be done with it.

( http://en.wikipedia.org/wiki/Plane_(Dungeons_&_Dragons)#Mirror_Planes )

Darth, your link is broken. In the URL tag, you don't put the text you want in the tag, you put it between the tags, like this:

Plane

Great reference, by the way.

 

[Christian]

Yes a mirror reflects darkvision, because mirrors are mystical portals to a plane of mirrors and do not concern themselves with photons and wavelengths and reflect stuff because....the faq says so? <waves hands> Don't try to explain it with real world physics, just say "Its dark. You are eaten by a grue" and be done with it.

No kidding. Yes, in the real world, mirrors work by reflecting light across the normal to the tangent plane of the reflecting surface. Also, eyes work by refracting light through the lens and absorbing it on the retina; so, when you're the subject of an Invisibility spell, you're blind!.

Don't think about it so hard. When you view a scene with darkvision, you see whatever you would see (other than color) if the whole scene were lit with sunlight up to 60' away from you. When you have See Invisibility running, you view the scene as if all of the invisible things were visible. Trying to make it more complicated just sends you down a slippery slope without Slippers of Spider Climbing.

 

[lukelightning]

If mirrors work with darkvision, how do pre-adolescent dwarves at camp scare themselves with Bloody Mary?

 

[sdt]

I like the idea of requiring special darkvision mirrors. The rules don't need to be so simple that a little science can't be applied once in a while. It's not game breaking in any case; unless we're talking about a Mirror of Life Trapping or Mirror of Opposition put in the dark to trap the characters with Darkvision.

 

[Nail]

How well does a piece of silvered glass reflect heat compared to light, though?

Well enough to matter.

If I sit a mirror near a fire, the mirror gets warm... so it's absorbing and transmitting heat as well as reflecting it, no?

Sure! And given the longer wavelength of thermal radiation, as well as the ability of most matter to absorb much of it, the reflected image will look blurry and dim, at best.

But since darkvision isn't infravision (or ultravision!! -- remember that?), it's all moot.

 

[SlagMortar]

If I sit a mirror near a fire, the mirror gets warm... so it's absorbing and transmitting heat as well as reflecting it, no?

I would guess that at least part of the warming comes from convection through the air, not from the absorbtion of infrared light.

 

[tzor]

If I sit a mirror near a fire, the mirror gets warm... so it's absorbing and transmitting heat as well as reflecting it, no?

Well yes and no. You see it's time for White Body / Black Body physics! (As opposed to White Mage / Black Mage physics.) A mirror is an imperfect white body.

A black body absorbes all radiation that hits it and emits radiation based solely on its temperature using a nice curve and as a result is called "black body radiation."

The sun is (oddly enough) a good example of a "black body."

A white body reflects all radiation that hits it and never emits any radiation on its own. It could be infinitely hot and you would never know, unless of course you touched it.

A true perfect mirror would be a white body, unable to emit any temperature it obtained by being next to the fire. No mirror is true and thus it both absorbs some radiation (thus making the image darker) and emits some radiation.

End of physics discussion.