# Does a mirror reflect all light including IR? **URL:** \ **Category:** Factual Questions\ **Created:** [January 8, 2012, 2:47pm UTC](https://boards.straightdope.com/t/does-a-mirror-reflect-all-light-including-ir/608821 "2012-01-08T14:47:11Z")\ **Posts on this page:** 11\ **Page:** 2
**Author:** ![notsoheavyd3](https://avatars.discourse-cdn.com/v4/letter/n/85e7bf/32.png) [@notsoheavyd3](https://boards.straightdope.com/u/notsoheavyd3)\ **Post date:** [January 8, 2012, 7:24pm UTC](https://boards.straightdope.com/t/does-a-mirror-reflect-all-light-including-ir/608821/21 "2012-01-08T19:24:15Z")
Of course that being said I’d expect him to feel the heat since last I checked there used to be a huge solar energy plant in the American south west that used alot of mirrors to collect energy and shine it on a tower. edit found it[http://en.wikipedia.org/wiki/Concentrated\_solar\_power](http://en.wikipedia.org/wiki/Concentrated_solar_power) ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [January 8, 2012, 7:40pm UTC](https://boards.straightdope.com/t/does-a-mirror-reflect-all-light-including-ir/608821/22 "2012-01-08T19:40:16Z")
> [@Chronos](#): > > And since the OP said _all_ light, it’s easy to make a mirror that will work reasonably well in visible, IR, and near UV (in fact, most mirrors will work reasonably well in that range without even being specifically designed for it), but beyond that, not necessarily. So far as I know, there’s no known way to make a gamma-ray mirror at all, for instance, and for far UV or X-rays, you usually have to settle for only a few percent reflectivity. [This says](http://uk.answers.yahoo.com/question/index?qid=20100509043206AA9QYZF)gamma ray mirrors exist. > [@](#): > > Since they have the shortest wavelength of all EM radiation, gamma rays are extremely deeply penetrating. > > Gamma ray mirrors do exist, but they are usually in the form of multilayer reflectors; sheets of reflecting material spaced by layers of gamma-transparent material. As a gamma ray passes down into the reflector, a succession partial reflections occur, one at each layer of reflecting material. A multilayer reflector is usually several metres thick, perhaps more, depending on the energy of the rays it works with. > > Multilayer reflectors of this nature are much more effective at shallow, grazing angles. For a gamma ray approaching it at a higher angle, less energy will be reflected. > > There are no theoretical limits to the efficiency of gamma ray mirrors, only engineering and economical concerns. The best attainable efficiency in practice probably peaks somewhere around 80% to 90%. ---
**Author:** ![Lynn\_Bodoni](https://avatars.discourse-cdn.com/v4/letter/l/e47c2d/32.png) [@Lynn\_Bodoni](https://boards.straightdope.com/u/Lynn_Bodoni)\ **Post date:** [January 8, 2012, 7:40pm UTC](https://boards.straightdope.com/t/does-a-mirror-reflect-all-light-including-ir/608821/23 "2012-01-08T19:40:32Z")
When my daughter was curious about how a TV remote worked, I told her about infrared. Then how infrared was a form of light that humans can’t see. She was about 8 or 10 at the time, and she’d also been curious about mirrors…so she pointed the remote at a mirror which reflected the image of the TV. Yep, the remote worked when its signal was bounced by the mirror. It wouldn’t work when it was pointed that way, but not at a mirror. ---
**Author:** ![constanze](https://avatars.discourse-cdn.com/v4/letter/c/f9ae1b/32.png) [@constanze](https://boards.straightdope.com/u/constanze)\ **Post date:** [January 8, 2012, 7:42pm UTC](https://boards.straightdope.com/t/does-a-mirror-reflect-all-light-including-ir/608821/24 "2012-01-08T19:42:03Z")
> [@notsoheavyd3](#): > > It’d depend. It’d depend on how much light the mirror was catching(IE how big) and if it focused it or spread it out. (Or if it was a flat mirror so did neither.) Flat mirror, because that’s what average people have in their purses (at least I think). Alternativly a watch face, such as kids use to make circles onto the blackbord on a sunny day. ---
**Author:** ![notsoheavyd3](https://avatars.discourse-cdn.com/v4/letter/n/85e7bf/32.png) [@notsoheavyd3](https://boards.straightdope.com/u/notsoheavyd3)\ **Post date:** [January 8, 2012, 7:46pm UTC](https://boards.straightdope.com/t/does-a-mirror-reflect-all-light-including-ir/608821/25 "2012-01-08T19:46:05Z")
> [@astro](#): > > [This says](http://uk.answers.yahoo.com/question/index?qid=20100509043206AA9QYZF)gamma ray mirrors exist. This link shows what they mean by a “mirror”. (IE it doesn’t so much as reflect as deflect) [http://astro.airynothing.com/2005/12/xray\_mirrors.html](http://astro.airynothing.com/2005/12/xray_mirrors.html) ---
**Author:** ![notsoheavyd3](https://avatars.discourse-cdn.com/v4/letter/n/85e7bf/32.png) [@notsoheavyd3](https://boards.straightdope.com/u/notsoheavyd3)\ **Post date:** [January 8, 2012, 7:47pm UTC](https://boards.straightdope.com/t/does-a-mirror-reflect-all-light-including-ir/608821/26 "2012-01-08T19:47:25Z")
> [@Lynn\_Bodoni](#): > > When my daughter was curious about how a TV remote worked, I told her about infrared. Then how infrared was a form of light that humans can’t see. She was about 8 or 10 at the time, and she’d also been curious about mirrors…so she pointed the remote at a mirror which reflected the image of the TV. Yep, the remote worked when its signal was bounced by the mirror. It wouldn’t work when it was pointed that way, but not at a mirror. You probably didn’t know this at the time but the camera in a typical cell phone can see that light. (You could have just had her look at it with a cell phone camera and push one of the buttons.) ---
**Author:** ![notsoheavyd3](https://avatars.discourse-cdn.com/v4/letter/n/85e7bf/32.png) [@notsoheavyd3](https://boards.straightdope.com/u/notsoheavyd3)\ **Post date:** [January 8, 2012, 7:49pm UTC](https://boards.straightdope.com/t/does-a-mirror-reflect-all-light-including-ir/608821/27 "2012-01-08T19:49:16Z")
> [@constanze](#): > > Flat mirror, because that’s what average people have in their purses (at least I think). Alternativly a watch face, such as kids use to make circles onto the blackbord on a sunny day. I’d expect a little mirror in a purse he’d feel because it should be big enough. Of course as long as it’s directed at bare skin. The watch probably wouldn’t work because it’s actually round and would spread out the energy. (And it’s smaller to boot.) ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [January 8, 2012, 7:53pm UTC](https://boards.straightdope.com/t/does-a-mirror-reflect-all-light-including-ir/608821/28 "2012-01-08T19:53:28Z")
> [@Lynn\_Bodoni](#): > > When my daughter was curious about how a TV remote worked, I told her about infrared. Then how infrared was a form of light that humans can’t see. She was about 8 or 10 at the time, and she’d also been curious about mirrors…so she pointed the remote at a mirror which reflected the image of the TV. Yep, the remote worked when its signal was bounced by the mirror. It wouldn’t work when it was pointed that way, but not at a mirror. My guess is it’s the hard surface, not the reflective layer, that bounces the remote signal. I have experimented with remotes bouncing off non-mirrored, not shiny, but hard, wooden walls, and they worked. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 8, 2012, 7:56pm UTC](https://boards.straightdope.com/t/does-a-mirror-reflect-all-light-including-ir/608821/29 "2012-01-08T19:56:13Z")
Kudos to your daughter, **Lynn**! That shows both more scientific aptitude in general, and more understanding of mirrors, than the typical college freshman (and no, I’m not exaggerating). **astro** , thanks for the information about gamma mirrors-- I hadn’t heard of those before. **notsoheavyd3** , with radio, the major issue isn’t the material (pretty much anything conductive will work), but with the size: You have to have a mirror significantly larger than the wavelength. And **constanze** , we’re assuming that you can feel the radiant heat directly from the Sun, right? The only reason I can think of that the sunbather might not be able to feel it on his back, too, is that you’d probably have a smaller area illuminated. I’d still expect that he could, though. ---
**Author:** ![constanze](https://avatars.discourse-cdn.com/v4/letter/c/f9ae1b/32.png) [@constanze](https://boards.straightdope.com/u/constanze)\ **Post date:** [January 8, 2012, 8:07pm UTC](https://boards.straightdope.com/t/does-a-mirror-reflect-all-light-including-ir/608821/30 "2012-01-08T20:07:51Z")
It’s just that while I did reflect light circles of my watch face\* onto the walls, I never experienced them on the skin, and neither other reflections of sunlight, so I’m unsure on whether the sunbather would feel it, or how much (depending on size, not quality of the mirror?) - the cheap Quartz watches have flat glass faces, though ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [January 8, 2012, 8:19pm UTC](https://boards.straightdope.com/t/does-a-mirror-reflect-all-light-including-ir/608821/31 "2012-01-08T20:19:08Z")
> [@Lynn\_Bodoni](#): > > When my daughter was curious about how a TV remote worked, I told her about infrared. Then how infrared was a form of light that humans can’t see. She was about 8 or 10 at the time, and she’d also been curious about mirrors…so she pointed the remote at a mirror which reflected the image of the TV. Yep, the remote worked when its signal was bounced by the mirror. It wouldn’t work when it was pointed that way, but not at a mirror. walls that are not dark also reflect enough light to work. quality remotes provide more than one LED so that there are many reflected paths and it is hard to not have it work. [Previous page](https://boards.straightdope.com/t/does-a-mirror-reflect-all-light-including-ir/608821.md?page=1)