cell_morph - Lab 3: Cellular Morphology and the Microscope...

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Lab 3: Cellular Morphology and the Microscope Laboratory Three: Cellular Morphology and the Microscope In lab two you learned that there were two types of morphology associated with single-celled microorganisms: cellular and colonial morphology. You also learned how to describe the colonial morphology. Now it is time to learn the cellular morphology of microorganism and about microscopy. A microscope is typically required to view the cellular morphology of microorganisms. The compound light microscopes are most frequently used by microbiologists for observing cells. The four commonly used varieties of light microscopes are the brightfield, phase contrast, fluorescent and the dark field. More advanced microscopes can also be used to view more details associated with cells and structures. These include the scanning and transmission electron microscope, atomic force microscope, and the confocal laser microscope. This laboratory is going to focus on the compound light microscopy techniques and specifically the brightfield and phase contrast. All light microscopes utilize the same basic principle. Light is produced by a light source and it is focused into a specimen on a glass slide. An image is produced as light is diffracted by the specimen. The image is magnified by a series of lenses, focused and sent to the eye. Magnification refers to an increase in the apparent size of the object displayed by the microscope and resolution refers to the ability to discern two objects as separate and distinct. Most light microscopes have a limit of magnification of 1000X. Lenses that focus light are not capable of producing a clear image of an object with high resolution when the object is magnified higher than 1500X. When the magnification produced by a light microscope approaches 1500X the resolution is often too low to produce a reliable image. This is due to the fact that glass or quartz lenses cannot gather enough light to produce a clear image. The ability of a lens to gather light is called its numerical aperture . Quality resolution is dependent on two things: the wavelength of the light (λ) and the numerical aperture (NA) of the lens. A simple formula applies when determining the smallest diameter (SD) of an object
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cell_morph - Lab 3: Cellular Morphology and the Microscope...

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