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What will the refractive index of infrared light traveling to air and through perspex be?

So n1 is air and n2 is the perspex, I am using Snell's law to prove that as thetha 1 decreases so will thetha 3. But I need to the refractive indices of IR though air and Perspex first. Are the values for n1 and n2 correct?

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    \$\begingroup\$ The values for N1 and N2 are correct for this type of problem. Now, if you need to hit a target the size of a pea with a laser shot from earth, after passing through an acrylic sheet at an angle, then maybe you need to use different values. But otherwise, you are fine. \$\endgroup\$ – mkeith Nov 3 '18 at 17:40
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    \$\begingroup\$ I really don't think this is an EE question... \$\endgroup\$ – Hearth Nov 3 '18 at 17:57
  • \$\begingroup\$ @Felthry, I am on the fence about it, too. At first I thought maybe it could have something to do with fiber optics. But now that it is updated, it seems more like physics. \$\endgroup\$ – mkeith Nov 3 '18 at 19:15
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According to this site, the index of refraction of acrylic is as follows:

enter image description here

Of course the index of refraction of air is 1.

Edit: By 1, I mean very close to 1 (as it is in a vacuum). If you're interested in the tiny variations from that this NIST site has some equations, but the variations will be much larger in the index of refraction of acrylic, so that will dominate the relative change when the light enters the acrylic from air (or vice versa). Not all acrylics are exactly the same. Wikipedia gives a range of 1.490–1.492 for acrylic, which is around an order of magnitude greater.

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    \$\begingroup\$ I was about to post basically the same thing. Just in case that site goes dead some day, the reference given there is: S. N. Kasarova et al. (2007) "Analysis of the dispersion of optical plastic materials" Optical Materials 29, 1481-1490 \$\endgroup\$ – mkeith Nov 3 '18 at 17:03
  • \$\begingroup\$ Would not refractive index be different for IR light through air? \$\endgroup\$ – Joey Nov 3 '18 at 17:07
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    \$\begingroup\$ The index of refraction for most wavelengths in air is 1. Absorption may occur. Can you (the OP) explain what you are doing, or why you want to know this? It may help us decide whether other things may be worth considering (such as dust and water vapor). \$\endgroup\$ – mkeith Nov 3 '18 at 17:21
  • \$\begingroup\$ @mkeith - I have updated the question. \$\endgroup\$ – Joey Nov 3 '18 at 17:26
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    \$\begingroup\$ @Joey very slightly but basically air is the same as a vacuum which is 1. See my edit. \$\endgroup\$ – Spehro Pefhany Nov 3 '18 at 17:27

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