infrared

[Ice_Phoenix87]

what materials does infrared not go through??

thanx

[Primarygun]

Glass blocks( don't know absorb or reflect) infrared radiation act an important part in greenhouse gases.

Carbon dioxide also, it absorbs.

[pulkit]

Glass does not specifically block infra red. It only blocks radiation above a certain wavelength. If glass were completely blocking infra red then there would be no green house effect.

[Primarygun]

there would be no green house effect.

Why?

[pulkit]

Because if glass were fully blocking infra red, it won't be able to get into the enclosure in the first place.

What happens is that IR gets into the enclosure, loses energy, hence wavelength increases and is then unable to escape - this is what u call greenhouse effect.

[5614]

red light and infa red are very similar, because the frequency of infa-red is slightly less than red light, and the wavelength is slightly more than red light's. because of this, they act similar, although not identically.

 

IR travels through air, glass [but only at certain angles, if it enters at more than the critical angle, total internal reflection happens, i.e. it gets stuck in the glass, read the above posts]

 

did you have a particular object in mind? it doesnt travel through solid objects, as X-rays, gamma rays can, and it doesnt really refract normally, like radio waves do.

[Primarygun]

Sorry I haven't learnt waves yet, just learn some geography.

Are all waves except sound waves reflect by object and have a refractive index?

[Ice_Phoenix87]

so something like alu foil would stop it?

[5614]

um, you havent learnt waves, that makes it hard!

 

all waves do everything, just it has to be in the right condition.

 

at this stage, i think that it is easier if you just accept that infa-red you cant see, it acts similar to light, especially red light because it just does!

 

and also just accept that light can get stuck in a glass box, and therefore so can IR. thats what other people were talking about earlier.

 

in the uk, you learn this stuff in year 10, when you are 14 or 15, but i dunno what country you are in, so i cant say for definate

[5614]

so something like alu foil would stop it?

 

yes

[pulkit]

I would have doubts about Al foil.

Al foil absorbs IR, it heats up. As it is now hot, it also radiates out IR, not a very suitable option !

 

The best way to protect something from EM waves (like IR radiation) is to use a simple faraday cage........no EM waves can exsist inside those.

[swansont]

Because if glass were fully blocking infra red' date=' it won't be able to get into the enclosure in the first place.

What happens is that IR gets into the enclosure, loses energy, hence wavelength increases and is then unable to escape - this is what u call greenhouse effect.[/quote']

 

Right mechanism, but it can start out as visible and UV. So the windows can be opaque at IR and you will still get the greenhouse effect.

[swansont]

IR travels through air' date=' glass [but only at certain angles, if it enters at more than the critical angle, total internal reflection happens, i.e. it gets stuck in the glass, read the above posts']

 

TIR only happens for light entering a medium of lower index, so it will never happen for light going from air to glass. It will occur if light tries to exit glass at certain angles, which is how multimode optical fiber works.

[swansont]

Al foil absorbs IR' date=' it heats up. As it is now hot, it also radiates out IR, not a very suitable option !

[/quote']

 

True of all materials that approximate a blackbody.

[5614]

TIR only happens for light entering a medium of lower index, so it will never happen for light going from air to glass. It will occur if light tries to exit[/i'] glass at certain angles, which is how multimode optical fiber works.

 

yes obviously, what i meant was that IR would entre the glass, then try to exit, at which point, if beyond the critical angle, TIR would occur

[Primarygun]

I heard that wrapping a book or a coat which are labelled with some anti-stealing things with an aluminium foil could leave the entrance of the shop.

How does it work?

[YT2095]

blue or green filters also work quite well, try it on your TV remote!