Earth Optics Video 2: Cross Polarized Light

In this video, I introduce techniques used in cross polarized light. Topics include: birefringence & extinction angles.
For supplemental questions and resources, please check out my webpage at www.earthopticsmineralogy.com
Michel-Levy Chart Used: University of Liverpool. D Flinn G Newall

[@angelaara8241]

you literally save my life with these videos

[@justinedvm]

wow you explained this so simply. thank you!

[@philipseven9215]

This is so helpful! I really hope to see more from this channel.

[@theOneGuy113]

Outstanding video! Very high quality and clear presentation. Helped a lot in understanding birefringence. Currently doing a petrography class.

[@deepakbellur9676]

You've done a wonderful job! Thanks !

[@shivamsoniiitb]

Really nice explanation loved it ☺☺🙏🙏Thank you so muchhh🙏🙏

[@1.4142]

Underrated!

[@ahmedaziz6062]

literary the best one, thanks.

[@horacioolgaolga302]

Estou gostando do vosso trabalho, tem me ajudado muito porque também trabalho nesta área

[@IpremiumSsarcasmi]

Thanks for teaching us photosynthesis.

[@yonkromis7883]

very interesting you have a pleasant voice and I'm trying to make some cross polarized sunglasses for solar or maybe they would be helpful in your line of work hopefully they are adjustable

[@johngauthier7576]

please make more vids!!!

[@ayubirana]

My Professor explained bunch of what I call "hee hee haa haaa" that made absolutely no sense. Thank you for helping students like me.

[@EarthOpticsVideos]

Thanks for watching! Happy mineralogy-ing! :D

[@gustafhannibal]

In the book of Revelations the building materials of New Jerusalem are described.
All anisotropic. No diamonds or rubies for example.
That is 12/12 anisotropic.
That I find amazing.
(See ch. 21 from verse 19)

[@bujeetishaga8384]

Amazing video please upload more

[@Trowa71]

I think Hank Green could make a MicroCosmos type TH-cam series for polarized minerals, I'd watch the shit outta that.

[@SarojSingh-hy7dv]

Thank you!

[@roboticShoeLace]

why is re-tardation not pronounced correctly?

[@nathenperri2826]

Can the chart be used to also determin the thickness of a mineral if the thickness is unknown?

[@EarthOpticsVideos]

Great question Nathan! Short answer is yes. If you know the mineral you are looking at, and record the birefringence of your sample, you can use the Michel-Levy chart to roughly determine the thickness. To more precisely measure thicknesses of objects in thin section (minerals, melt/fluid inclusions, bubbles, etc.), I prefer to use a microscope with a calibrated focus knob. For this method, I put the top of the object in focus, take note of the measurement on the focus knob, turn the knob to put the bottom of the object in focus, and take note of the new measurement on the focus knob. The thickness of your object is the difference between the two measurements. I hope this helps - please let me know if it is unclear or if you have questions. This sounds like a good idea for a new video... :)

[@nathenperri2826]

@@EarthOpticsVideos Thank you very much for your reply. Your explanation is very clear, and I will deffinatly test out both of those methods.

[@DeepakGupta-ce3jv]

Mam, My sample is liquid crystal and the sample thickness is 3.3 micrometer. And I think I am getting second order colours. But the line extending from 3.3 micrometer cannot cut this colour. can you please tell me how to find birefringence in this situation. Or is it impossible to get second order colors in this thickness?

[@EarthOpticsVideos]

Hi! Although I'm not too familiar with liquid crystal properties, you can always calculate birefringence by the relationship: Retardation = thickness x birefringence. You can determine the retardation by noting the interference color you observe and referring to the bottom x-axis on a Michel-Levy. Since you know your thickness, you can solve for birefringence.

[@nuraizulazren7673]

what is the definiion of cross polarized light XPL ?

[@EarthOpticsVideos]

As polarized light passes through an anisotropic medium, light splits into a fast and slow component that vibrate perpendicular to each other. Inserting a cross-polarizing filter (aka the analyzer) between your sample and your eye recombines (think vector addition) the fast and slow waves of light by only allowing one vibrating direction through. Check out figure 3 in this write-up by Olympus: www.olympus-lifescience.com/en/microscope-resource/primer/lightandcolor/birefringence/ Hope this helps! Happy Microscoping :D

[@natureforestbeauty]

Nice

[@SalvableRuin]

The Book of Revelation says the foundation of the New Jerusalem will be "adorned with all kinds of precious stones," all 12 of which are anisotropic: jasper, sapphire, chalcedony, emerald, sardonyx, sardius, chrysolite, beryl, topaz, chrysoprase, jacinth, and amethyst. (Revelation 21:19-21)

[@valentinacorrea8333]

Video espectacular, solo me falta entender inglés 🥺

[@J1hn1]

Very good, thanks! But speaking to fast sometimes and the last example could be more educational

[@EarthOpticsVideos]

Thanks for the feedback!