While lighting off 4th of July fireworks, I begun to wonder a few things. I forgot to ask my Grandfather (a former physics teacher), so I thought I may ask them here…
Would infared goggles allow one to see through smoke? Why or why not?
Is it possible to develop tools to see ultraviolet light like we do infared or visible? Are there any practical applications of such a thing?
Hi Opal!
Thank you so much for your responses!
Infrared would certainly see better through smoke than visible light. Smoke is made up of a bunch of tiny solid particles suspended in transparent gasses-- It’s the solids that make it opaque. Due to the wave nature of light, light can basically ignore obstacles smaller than about the wavelength of light, and infrared has a longer wavelength than visible light. There might still be some smoke particles bigger than the wavelength of infrared, though. I don’t know what the typical size distribution would be.
On your second question, astronomers and physicists will often take images in the ultraviolet, usually because some star or other object has spectral lines of interest somewhere in the UV. Of course, these images are presented in false color when people actually look at them. I’ve never heard of such a system being used in a headset or goggles or the like, although I don’t see any reason it couldn’t be done.
Of course, wearing UV goggles wouldn’t give you much to look at unless you had a UV flashlight strapped to your head (as in night vision goggles). High-energy (ionizing) radiation is pretty rare, which is good: If we’re constantly being bathed in radiation that can tear up our proteins and genetic information, we’re going to be dropping like flies.
Interestingly, if you want to photograph fireworks effects, putting an ultraviolet filter over your camera lens can make visible light seem brighter and sharper.
Interestingly, if you want to photograph fireworks effects, putting an ultraviolet filter over your camera lens can make visible light seem brighter and sharper.
Same goes for most decent pairs of sunglasses.
Note that “infrared” covers a large territory. Near infrared goggles are basically seeing the same thing as red light (it’s just a bit off the end of human eye frequency sensitivity). In that case, if trying to see through smoke by using a red filter doesn’t help you, then using a near-IR scope won’t help much either.
Things are different if you’re using a “thermal” IR converter such as a cooled FLIR or bolometer array. Those frequencies are many times longer than visible light, therefore the particles in the smoke will “act smaller” and scatter the light much less.
I’ve heard that the longest of longwave IR goes right through wood, paint, and sheetrock as if it was like glass (which means that most of us are living in “glass houses”, and thermal IR scopes make for an interesting viewpoint.)