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23 Cards in this Set

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