How to do Polarization Microscopy

hi everyone welcome to my new channel micrographia today i'll be showing you a video about polarization on the microscope how the technique works and how you can do it too i really hope that you enjoy my video setting up your first polarizing microscope is really easy all you need are two polarizing filters one sits in the space between the head and the nose piece of the microscope and doesn't move you just leave it up there the second polarizing filter is called the polarizer it sits over your field condenser lens and is rotated for the effect some microscopists like to put their analyzer directly over the specimen on the glass itself i prefer to do it this way but you can do it any way you like that works light from a light source normally wiggles multi-directionally polarized light travels in a unidirectional fashion polarizing filters are made of polyvinyl alcohol plastic which is stretched to produce long parallel chains at regular intervals iodine is then added to these chains which allow the chains to absorb light light traveling parallel to these chains will be absorbed by the filter whereas light traveling perpendicular to the filter will be allowed to pass through since light only traveling in the perpendicular fashion is allowed through the filter on the other side of the filter you have polarized light traveling in a single direction towards your specimen i mentioned the light wiggling because it's the orientation of the light on an axis which is important in polarization microscopy adding a second polarizing filter will block out more light depending on its orientation and when the polarizers across totally a phenomenon called extinction occurs which may be more or less pronounced depending on the filters you have your filters will likely not create total extinction but allows some light wiggling nearly in the same axis to create an image in the ocular lens polarizing filters can be easily obtained on ebay or amazon typically the best polarizing filters for microscopy will be called linear polarizers on ebay you can acquire linear polarizers that are measured and often meant for microscopes they work pretty well and that's what i use although you can find sheets of linear polarizing film of varying qualities from multiple sources and i suggest looking into what product you think will be the best for you alternatively if you'd like to save money polarizing filters can be fashioned out of all kinds of things such as polarizers found on camera attachments you could get it out of a 3d movie glass film even old handheld video game consoles such as a game boy color can have their screen taken apart and the polarizer removed for use in microscopy you can get creative in finding polarizers because they're actually quite common birefringence is formally defined as the double diffraction of light in a transparent molecularly ordered material which is manifested by the existence of orientation dependent differences the crystalline lattices that produce the polarization effect seen in images can include things like epsom salt many different types of acids and living structures such as chloroplasts and diatoms these are called anestropic crystalline lattices things that don't produce the effect are called isotropic optically and those can include things like table salt glass or anything else that doesn't have any strain and this is why many objectives you buy from microscope dealers that are marked as pull are marked in this way because the glass produced for these microscope objectives don't contain any strain you may be wondering how those incredible colors are produced because of birefringence which i mentioned previously light is split in the crystal causing one ray to be relative to the other and when they join at the analyzer produce interference colors this is the basis for the colors produced in polariscopy images next i would like to show you how to make slides of your own i'll start with epsom salt as it's often the simplest and easiest household chemical to work with to start you should mix about one teaspoon of epsom salt into 250 to 300 milliliters of warm water next agitate the mix until the crystal is fully dissolved within solution following this take a pipette or other implement and take a few drops of the solution spread it evenly over a pre-wash slide across the whole surface next you'll want to form a thin crystalline layer of the epsom salts on the slide by drying it over heat i usually do this by holding the slide over a tea light about 1.5 inches from the flame it's important to be patient doing this because you don't want all your crystals to form in one spot on the slide nor do you want to burn them especially if you're working with crystals that are easily combustible now you have a complete slide ready for viewing underneath your microscope epsom salt always produces interesting and varied results another popular way to view crystals is to use something called wart remover it's concentrated salicylic acid in a powerful solvent i should express a word of caution when using salicylic acid as it's very corrosive on the skin it should be used only with the proper personal protective equipment such as gloves and a smock or any other kind of full-length clothing to protect your skin my preferred method to make slides with salicylic acid is to use two slides where one is flipped over and used to spread the salicylic acid over the other slide in a thin layer and as quickly as possible to avoid it prematurely drying you can now watch the crystals forming on the slide in real time isn't it amazing if you aren't comfortable working with harsh chemicals or open flames another method you can use is taking vitamin c for example from a vitamin c caplet if using a vitamin you'll have to grind the vitamin up and allow it to sit in a solution overnight to get the chocks and binding agents out of your solution following that just take a pipette or something similar to that and being careful not to disturb the solution spread it out over your slide again once you have done so you can just leave the slide to dry overnight here citric acid can sometimes be obtained from grocery stores and you may find this easier to work with congratulations now you have a few different ways to make slides there are many other ways to do it too using many other different chemicals and i hope you have a lot of fun exploring all the different kinds of ways you can view crystals underneath a microscope i really don't think this video would be complete unless i showed you some of the images i've been so lucky to capture over my short time working with this [Music] technique [Music] do thanks so much for watching this video and if you've gotten this far i'd like to encourage you to use these methods for yourself and please comment any questions you might have and i'll do my best to answer them if you liked my video please give me a thumbs up and subscribe for more content about microscopy and other fascinating scientific topics i hope to catch you next time i'd also like to thank those that supported me in the last year as i grew to love microscopy and learn to use microscopes thank you so much [Music] you

Channel: Micrographia

Views: 14,361

Keywords: science, microscopy, polarization, crystals, micro, colorful

Id: XTHBrV8mONk

Length: 8min 34sec (514 seconds)

Published: Tue May 19 2020