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Published byKameron Rumley Modified over 9 years ago
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IFFAT FATIMA UOG
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ELECTRON MICROSCOPE
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Contents History LM Vs EM Electron microscope Principle Types of EM Application & importance
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History of Microscope 1590-tube microscope by dutch glass maker 1665-Robert hooke’s microscope
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Continued…………………………… 1674-Antonee van leeuwenhooke TEM co-invented by Ernst Ruska (1931)
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Main characteristics of microscope Resolution
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Magnification
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Light Microscope Vs Electron microscope
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Comparison Light microscope Resolution: 0.2μm to 200nm Magnification: 2000x Illumination: Light Glass lenses Objects seen: frog's egg cells‚ cell wall‚ cilia‚ flagella‚ nucleus & other organelles etc. Living specimen Lower resolving power Focus: condenser lense Electron microscope Resolution: 0.2nm Magnification: 2‚000‚000x Illumination: Electron Electromagnetic lenses Objects seen: orgenelles‚ proteins‚ viruses‚ small molecules etc. Dead specimen Higher resolving power Focus: vaccum & magnetic lense
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Electron microscope Electron microscope is a scientific instrument that uses a beam of energetic electrons to examine objects on a very fine scale. Why electron beam? Wave nature of particles
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Types of Electron microscope
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Transmission electron microscope Instrumentation Electron Source Electromagnetic lense system Sample holder Imaging system
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Working Emission of a high voltage beam of electrons. Focusing of beam on specimen. Transmission through the specimen. Magnification of the image. Recording of the image by fluorescent screen, light sensitive sensor (camera).
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TEM
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Sample preparation Fixation Rinsing Post fixation Dehydration Infiltration Polymerization Sectioning
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Applications Ultra-structure analysis Crystal structure
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Scanning Electron microscope Emission of a beam of by an electron gun. Passage of electron beam through the vacuum. Focusing of beam down toward the sample. Ejection of X-rays & es. From sample after hitting. Collection of by detectors & conversion to a signal. Transmission of signal to a screen/ final image
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Scanning EM
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Sample preparation Metals require no preparation Non metals require coating of a thin layer of conductive material.
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Applications Medical & physical science Semiconductor industry Examination of a large specimen range.
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Any Q?
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