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Actually I had asked in another post that "Does infrared rays pass through active shutter glass" but someone just commented that infrared rays dont pass through polarized glass. If infrared rays doesnt pass through polarized glass can someone explain the reason or give reference link to look through.

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2 Answers 2

Infra-red radiation will pass through a polarised medium just like visible light does i.e. the component at right angles to the plane of polarisation will be blocked. So there's nothing special about the fact the glasses are polarised.

However most materials are only transparent over a restricted range of wavelengths. Optical glass only transmits light with a wavelength from about 300nm to around 2500nm. There's a good article on the optical properties of glass here.

However I think passive 3D glasses are made from conventional polarisers, which are made from a polymer called polyvinyl alcohol. I struggled to find much about the spectra of PVA polarisers, though I found this article that lists some polarisers that work down to 3000nm. So it seems PVA polarisers will transmit at least the near infra-red. However the term infra-red covers a huge range of wavelengths from 750nm - 1mm. I can't think of anything, even air, that is transparent right across this range of wavelengths so everything absorbs infra-red light to some extent.

Generally speaking, ultra-violet light is absorbed because it has enough energy to excite the electrons in atoms and infra-red light is absorbed because it has the right energy to excite molecular vibrations. Visible light has too much energy to excite molecular vibrations, but too little to excite electrons in atoms, so that's why most things are transparent to visible light (and probably why organisms like humans evolved to use it). Most things that are opaque, like say paper or chalk, don't absorb the light but scatter it by multiple reflections at air/solid interfaces. The exceptions are things like transition metal complexes and organic dyes.

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Yes, infrared light get pass through two polarized films (vertical & horizontal) even those films are 90 degree rotated.

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Hi Kiran, some physical justification for a "yes" answer would be nice. –  Brandon Enright Dec 4 at 5:31

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