Microscopy
Microscopy
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Technique to study cells, tissues, and small organisms
Morphology
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Size, shape, and structure of cells, tissues, and small organisms
Zacharias Janssen
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Dutch maker of one of the earliest compound microscopes
Antonie van Leeuwenhoek
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Maker of simple microscopes with one lens
Light
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Visible electromagnetic radiation detected by the human eye
Optical Microscopy
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Uses glass lenses to magnify and focus light
Scanning Probe Microscopy
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Uses a mechanical probe to feel the surface of the specimen
Uses of Optical Microscopes
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Illuminate, magnify, generate contrast, resolve, and capture images
Principle of Optical Microscopy
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Uses lenses to focus light onto the specimen and collect the image
How Does a Light Microscope Work?
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Light is focused onto the sample and magnified through lenses
Components of Light Microscopy
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Light source, diaphragm, condenser, stage, focus controls, objectives, eyepiece, camera
Example Uses of Light Microscopy
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Determining cell presence, cancer stage, subcellular structures, molecules, and proteins
Magnification
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Combination of eyepiece and objective lenses
Resolution
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Minimum distance at which two distinct points can be seen
Numerical Aperture
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Measure of light-collecting and resolving power of a lens system
Refraction
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Bending of light between different media
Refractive Index
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Matching refractive indices to increase resolution
Limits of Resolution
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Anything smaller than 200 nm cannot be resolved using light microscopy
Fluorescence Microscopy
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Using specific spectra to detect fluorescent molecules
Epifluorescence Microscopy
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Floods the entire sample with light to capture both in-focus and out-of-focus light
Confocal Fluorescence Microscopy
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Exposes a specific part of the sample to light and uses a pinhole to focus emitted light
Electron Microscopy
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Uses electromagnetic/electrostatic lenses to magnify and focus electrons
Transmission Electron Microscopy (TEM)
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Images thin samples by passing electrons through the sample
Scanning Electron Microscopy (SEM)
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Images thicker samples by detecting emission of secondary electrons from the surface
Disadvantages of electron microscopes
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Bulkier, expensive, and cannot image live cells