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the micro basics

  1. micrometer
    • (micron)
    • 1 millionthof a meter, "um"
  2. nanometers
    1 billionth of a meter, designated as nm
  3. Basic system in micro-biology
    • light microscope aka compound microscope
    • it uses two lenses
    • objective lens: nearer the object ocular
    • lens: nearer the eye
  4. mechanics of light microscopy
    • light passes into substage condenser
    • condenser focuses light into a sharp cone
    • light passes through stage into slide and bounces off object
    • objective lens captures light forming a “real image”this image travels to ocular lens, magnifying it again to form the virtual image
  5. low power
    10X
  6. high power
    40X
  7. oil immersion
    100X
  8. Resolving Power
    • (RP) Lens system must transmit light without variation and allow closely spaced objects to be clearly distinguished
    • RP determines the size of the smallest object that can be seen clearly with a given lens
    • RP = wavelength of white light / 2NA wave length of white light is 550nm
    • NA = numerical aperture of lense
  9. Working Distance
    • amount of clearance between slide and bottom of objective
    • larger power of objective lens means less working distance
  10. Oil immersion lens
    • light (because of low refractive index) bends abruptly when leaving glass side and entering air
    • low and high power objectives wide enough to still capture light
  11. Simple Stain
    • since cytoplasm has a negative charge, and basic dyes have apositive charge
    • dye attracted to cytoplasm of cell
  12. Negative Stain
    stains the background, and not the actual organism
  13. Gram Stain
    • a very valuable way to subdivide organisms
    • this is used as a preliminary step to identifying unknown organisms
    • differentiates bacteria into two group so
    • Gram positive stains: blue (ends purple)
    • Gram negative – stain red (ends pink)
  14. Dark-field microscopy
    background remains dark while object illuminated
  15. Phase-Contrast Microscopy
    • light beams split so rays are slightly out of phase
    • separated beams of light pass through and around object
    • small differences in densities show up as variation of brightness and contrast
    • advantage: can view living organisms without staining
  16. Fluorescence Microscopy
    organisms coated with fluorescent dye (i.e.:fluorescein) and illuminated with UV light
  17. Transmission Electron Microscope
    • Used to photograph detailed structures within cells
    • Need ultra thin sections of material so electrons can penetrate
  18. Scanning Electron Microscopy
    Used to see surfaces of objects in natural state without sectioning
Author
brogdert
ID
54712
Card Set
the micro basics
Description
microscope
Updated

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