[Music] how does such a microscope work the optical microscope has been known since the 17th century the modern optical microscope has magnification of about 10,000 times and makes it possible for the human eye to distinguish objects that are two ten thousandth of a millimeter away from each other it is this resolving power of the microscope ie the ability to distinguish two very close objects in an image which is one of the most important parameters the level of magnification just makes it possible to picture how the image was enlarged however it does not say whether we can see anything in the picture a human eye at its best has only a resolution of 0.2 millimeters while the optical microscope has two ten thousandth of a millimeter and the electron microscope has up to fifty Pico meters wait a minute that's too many numbers well it's as if you were watching a tennis match from the moon and we're still able to follow the small tennis ball hmm interesting let's go back to the optical microscope when attempting to reach a better resolution scientists encountered the limits of the wavelength of the light used for the elimination of the sample it was not possible to distinguish points closer than several hundreds of nanometers in 1920 it was discovered that accelerated electrons in a vacuum can act as light while the wavelength of these electrons is about 100,000 times smaller than light it was also discovered that electric and magnetic fields influence electrons similarly to how lenses and mirrors influence the light Hey who is this handsome fellow that's dr. Ernst Ruska who assembled the first electron microscope in 1931 and after more than 50 years he was awarded the Nobel Prize for Physics for his invention well the main thing is that he lived to receive it I am still waiting I would still like to know what an electron actually is an electron is the negatively charged particle of an atom orbiting around the nucleus it can be released by or an electric field electrons are 2,000 times lighter than the smallest atom thus they can easily be stopped or diverted when hitting materials now I see that's why there must be a vacuum in the microscope great the column of the electron microscope consists of basically the same parts as the optical one however the source of light is replaced by the so called electron guns and the glass lenses by electromagnetic ones the electron beam is produced by an electron gun in which for example a tungsten filament can be placed as the electron source the beam is produced by heating the filament up to 2,700 degrees Celsius and connecting it to high-voltage to higher the voltage the higher the energy of the electrons the electrons accelerated by three hundred kilovolts almost reached the speed of light however to reach a high resolution the accelerating voltage and series of lenses must be immensely stable the power cabinet contains a number of sources whose output voltage or current fluctuate not more than one millionth of the output value I probably understand but don't you have another example the one with tennis was excellent I do try to imagine that the allowed voltage fluctuation in a common socket has the height of Mount Everest then the allowed voltage fluctuation of a 200 kilovolt high voltage source as the height of only seven centimeters such stability needs very efficient and sophisticated electronic circuits you see how good you are with examples let's go on since electrons move freely only in a vacuum there must be a vacuum in the entire column to achieve this the vacuum pumps are used various levels of vacuum are needed the highest is around the electron gun the difference between common air pressure and residual pressure in the microscope is about 10 orders of magnitude so it means that the probability that an electron will hit an air molecule on this pressure when passing through the column is zero yes almost zero however dozens of millions to billions of electrons hit the samples per second poor lizard electromagnetic lenses focused the electron beam on the examined sample in an optimal way during its entire journey the electron beam goes through a number of apertures with various diameters the smallest ones can be just a few thousandths of a millimeter these apertures stop electrons undesirable for creating the image the electron beam hits the observed object and it either scans its surface step by step as if we were reading an inscription on the wall with a torch at night or it goes through the sample and shows its inner structure I see and according to the way the electron beam hits the sample we distinguish two basic types of electron microscope scanning and transmission exactly the sample for the transmission electron microscope is very thin several hundred nanometers and it is placed on a grid if it wasn't then electrons would be stopped and no image would be created in the transmission microscope there are various holders available for the examination of samples in the transmission markets but depending on the application a customer would like to use here we can see a holder where more samples can be placed at the same time on the other hand the sample examined in the scanning microscope can be bigger even dozens of centimeters [Music] therefore the scanning microscope is always used where information about this surface of the sample is required yes the only requirement is that the sample must withstand a vacuum and the irradiation with electrons a holder is not necessary samples are placed in a small table which is placed under the electron column as soon as the electron beam hits the sample or scans through it the various detectors placed in the microscope create the final image and can I manipulate the sample place this way in the microscope you are right that it is not enough to move most of the examined objects along a horizontal axis information can be gained from various depths of the sample and we can observe them if we slightly turn the sample the sample holder in no transmission microscope is inserted through a vacuum interlock in the goniometer this enables that not only movement along the x and y axes but also its inclination around one or both axes also the rotation or movement along the z-axis in parallel to the electron beam whew that sentence is a little complicated and would be enough to say yes it's possible we'd better move on what influences the quality of the picture the image quality in the scanning microscope depends on the orientation and distance of the sample from detectors and the final lens the stage on which the sample is placed makes it possible to move it vertically along the x and y axes up and down in the direction of the z-axis and with a possible inclination and rotation these movements are performed with step motors and are controlled by the computer great but show me some pictures already biologists use electron microscopes to examine the structure of cells bacteria viruses and colloidal particles scientists who are concerned with material characteristics wants to observe in Hommage entities and faults in metals crystals and ceramic material in geological fields the electron microscope allowed the detailed studies of rocks minerals and fossils and to understand the origin of our planet and its valuable mineral resources modern electron microscopes not only display but also analyze measure and modify in 2d 3d and even 4d weights I know it here this is say tech in Brno Central European Institute of Technology yes there is a kryos electron microscope here with a special function it can work with biological samples they would soon be dehydrated by the vacuum in the common electron microscope and thus would be destroyed for the research however Fei has developed a system where each sample is permanently frozen to at least the temperature of liquid nitrogen from its production to its examination in the cryos microscope I understand thus the damage is permanent Jiki transmission electron microscopy tightening trials we began a more premium detector and electron Falcon via Ducati Menasha laboratory at structurae Veeru Japan a protein OB complexes ville-marie second row station this constructor journalist organization in Russia pratical me to Vegeta protrusion emotionally obvious need nap ticket mechanism a in fact safety pedeu netball mechanism a AXA initely weak protein complex adjustment is due a GT velvetescape Okkadu huge punky ness me know we have a microscopic rio-são extraneous stability' Geronimo's near provided local vanishing attack emotional music playing automated scanners even Teddy besties Thomas J up slowly nakita mo mu gemenon is it clarity Nietzsche data we have got Co Josue attack affecting a visionary teachers priests Roy social induce let Cassandra national clad in a police car yet nice doctor [Music]
