Can anyone with a better understanding of optics help me out?

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Anonymous
2017-01-21 02:30:30 Post No. 8618818
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Anonymous 2017-01-21 02:30:30 Post No. 8618818 [Report]

Can anyone with a better understanding of optics help me out?
This isnt homework, obviously, but a practice test for my coming physics finals.

The question is:

>An engineer checks a part by shining white light in a 45° angle on a Silicate plate with an index of refraction of 3.9, which has a thin layer of Silicium-Oxide on the outside, with an index of refraction of 1.46.
>The thin layer shines in the correct kind of green, which proves to her that it has the correct thickness.
>a) How thick is the layer, if a wavelength of 560nm is assumed?
>b) Explain mathematically why she looks at it at an angle, instead of straight at it?

Now Im certain that this has to do with the fact that the index of refraction is dependent on the wavelength, and so the light will be split up into different angles for different wavelengths.
However I couldnt find a formula for that relation anywhere, and Im confused by the fact that the index is given as one specific number.
I will follow with what I have so far, but its not much.

Help greatly appreciated.

Anonymous 2017-01-21 02:33:37 Post No.8618819
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Anonymous 2017-01-21 02:33:37 Post No.8618819 [Report]

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Phonepost because lazy...

Anonymous 2017-01-21 02:34:00 Post No.8618820
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Anonymous 2017-01-21 02:34:00 Post No.8618820 [Report]

Put the question in google. You're welcome.

Anonymous 2017-01-21 02:41:37 Post No.8618832
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Anonymous 2017-01-21 02:41:37 Post No.8618832 [Report]

>>8618819
This is what Ive come up with:
>The light hits the first border, and the different wavelengths get separated.
>They then hit the second border, and get partially reflected at the same angle as the angle of incident.
>They hit the first border from the other side, and get refracted again.

But now they are all at the same angle as they were before,except on the other side of the normal.
All wavelengths are at 45°, but they are spaced apart slightly.

The angle is thus not related to the thickness of the layer, and I cant find the answer.

What am I missing? Does it have to do with total reflection upon hitting the first barrier the second time or something? I dont get it.

Anonymous 2017-01-21 02:58:26 Post No.8618859
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Anonymous 2017-01-21 02:58:26 Post No.8618859 [Report]

>>8618820
Believe me /sci/ isnt my first resort for this sort of stuff.
However I couldnt find anything neither on Wikipedia nor in my script that would explain what to do here.

Anonymous 2017-01-21 05:24:24 Post No.8619098
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Anonymous 2017-01-21 05:24:24 Post No.8619098 [Report]

Selfbump. Im still lost.

I'm aware that Imgur.com will stop allowing adult images since 15th of May. I'm taking actions to backup as much data as possible. Read more on this topic here - https://archived.moe/talk/thread/1694/

I'm aware that Imgur.com will stop allowing adult images since 15th of May. I'm taking actions to backup as much data as possible.
Read more on this topic here - https://archived.moe/talk/thread/1694/