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23 Cards in this Set
- Front
- Back
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What is the refractive index?
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The refractive index is a measure of how greatly a substance slows the velocity of light; the direction and magnitude of bending are determined by the refractive indices of the two media forming the interface
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Why does a glass prism bend light?
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Because glass has a different refractive index from air and the light strikes its surface at an angle
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What is the focal length?
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the distance between the center of the lens and the focal point
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How is lens strength related to focal length?
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Lens strength is related to focal length; a lens with a short focal length magnifies an object more than a lens having a longer focal length
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What type of microscopes are all modern microscopes?
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Compound microscopes
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What lens the objective lens?
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The lens closest to the specimen
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What type of microscope forms a dark image against a brighter background?
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Bright-field microscope
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What is a focal point?
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Where the light rays are focused
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In a bright-field microscope, what is the total magnification?
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The product of the magnifications of the ocular lenses and the objective lenses
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How does wavelength of light relate to resolution
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Shorter wavelength => greater resolution
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What is the working distance?
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The distance between the front surface of lens and surface of cover glass or specimen when it is in sharp focus
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What is the benefit of using immersion oil compared to just air?
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Many light rays that did not enter the objective due to reflection and refraction will now do so; increases the resolution and numerical aperture
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Which microscope produces a bright image of the object around a dark background?
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The dark-field microscope
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The dark-field microscope analyzes what types of organisms?
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Living, unstained preparations; like internal structures of eukaryotic microorganisms; and Treponema pallidum (syphilis)
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Which microscope converts slight differences in refractive index and cell density into easily detected variations in light intensity?
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The Phase-Contrast Microscope
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What type of cells does the phase-contrast microscope study?
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Living cells; microbial motility; bacterial structures
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Which microscope creates images by detecting differences in refractive indices and thickness of different parts of specimen?
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The differential interference contrast microscope (DIC)
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What types cells does the differential interference contrast microscope analyze?
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living cells; appear brightly colored and three dimensional
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What microscope exposes specimen to ultraviolet, violet, or blue light?
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The fluorescence microscope
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What microscope uses specimens stained with fluorochromes?
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The fluorescence microscope
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Which microscope is used to study biofilms?
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Confocal microscopy
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How does a confocal microscope work?
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It creates a sharp, composite 3D image of specimens by using a laser beam, aperture to eliminate stray light, and computer interface
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What are the benefits of staining specimens?
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Increases visibility of specimen
Accentuates specific morphological features Preserves specimens |
