Home
Flashcards
Preview
the micro basics
Home
Get App
Take Quiz
Create
micrometer
(micron)
1 millionthof a meter, "um"
nanometers
1 billionth of a meter, designated as nm
Basic system in micro-biology
light microscope aka compound microscope
it uses two lenses
objective lens
: nearer the object ocular
lens
: nearer the eye
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
low power
10X
high power
40X
oil immersion
100X
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
Working Distance
amount of clearance between slide and bottom of objective
larger power of objective lens means less working distance
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
Simple Stain
since cytoplasm has a negative charge, and basic dyes have apositive charge
dye attracted to cytoplasm of cell
Negative Stain
stains the background, and not the actual organism
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)
Dark-field microscopy
background remains dark while object illuminated
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
Fluorescence Microscopy
organisms coated with fluorescent dye (i.e.:fluorescein) and illuminated with UV light
Transmission Electron Microscope
Used to photograph detailed structures within cells
Need ultra thin sections of material so electrons can penetrate
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
2010-12-10T02:44:06Z
Show Answers
Home
Flashcards
Preview