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Micro Chapter 3
See pages 66-68 for summaries
Terms in this set (25)
compound light microscope
has a series of lenses that uses visible light as its source of illlumination.
the light source
part of the microscope that has lenses that direct the light rays through the specimen
the lenses closest to the specimen
objective lens magnification (power) X ocular lens magnification (power)
ability of the lenses to distinguish fine detail and structure. Also called resolving power)
a measure of the light-bending ability of a medium. Can be changed by staining a specimen.
the ability of the condenser to focus light onto the field of vision
used to examine specimens that are either invisible in the ordinary light microscope or cannot be stained. Uses a darkfield condenser that contains an opaque disk, which blocks light that would have entered the objective lens directly. Specimen appears light against a dark background.
permits detailed examination of living organisms. Does not require the microorganisms to be attached to slide or stained.
differential interference contrast (DIC) microscopy
uses two beams of light instead of one, and prisms split each light beam, adding contrasting colors to the specimen. Higher resolution than the phase-contrast microscope. Appears 3 dimensional.
microscope that uses ultraviolet light to cause specimens to give off light of longer wavelengths (and visible). If the specimen doesn't naturally fluoresce, it is stained with a group of dyes called fluorochromes.. Objects then appear luminescent against a dark background.
technique in light microscopy used to reconstruct three dimensional images. Uses a short wave blue light to illuminate one plane of the specimen at a time, which is then fed into a computer to generate a 3D image.
two-photon microscopy (TPM)
uses long-wavelength (red) light (two photons total). Allows imagining of living cells in tissues up to 1mm deep. Can also track activity of cells in real time.
scanning acoustic microscopy (SAM)
interpreting the action of a sound wave sent through a specimen
used to examine objects smaller than 0.2um. A beam of electrons is used instead of light-they are used to examine specimens too small to be resolved with light microscopes. Images are always black and white (although they can be artificially colored).
transmission electron microscope (TEM)
a finely focused beam of electrons from an electron gun passes through a specially prepared, ultrathin section of the specimen. This specimen is usually placed on a copper mesh grid. Final image is called a transmission electron micrograph.
use of stain applied directly to specimen to increase contrast of specimen (make it easier to see against background)
use of stain to increase the electron opacity of the surrounding field (useful for the study of the very smallest specimens)
a heavy metal is sprayed at an angle of 45 degrees so that it strikes the microbe from only one side. As it piles up, the uncoated area on the opposite side leaves a clear area behind it as a shadow. This gives a 3D effect and provides a general idea of the size and shape of a specimen
scanning electron microscope (SEM)
provides striking 3D views of specimens. Produces an image called a scanning electron micrograph. Do not need to view specimens in sections as in TEM
these use various kinds of probes to examine the surface of a specimen at very close range without modifying the specimen or exposing it to damaging, high-energy radiation.
scanning tunneling microscopy (STM)
uses thin metal (tungsten) probe to scan a specimen and produce an image that reveals the bumps and depressions of the atoms on the surface.
atomic force microscopy (AFM)
a metal and diamond probe is gently forced down onto a specimen. As the probe moves along its surface, its movements are recorded and a 3D image is produced.
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