Microscopy and Specimen Flashcards
Refractive Index
Measure of the speed of light through that medium, ratio therefore there are no units
Refraction
Light passing from 1 medium to another is bent if the two media have different refractive indexes
How do lenses work?
Focuses light, the curved class focuses light into a point
Resolution
The minimum distance between 2 objects where lens can distinguish 2 objects
Numerical Aperature
Property of each lens, and it increases so does the resolution
Bright field Microscopy
Darkens image, bright filled,
Condenser focuses light
View eukaryotic cells, bacteria “all purpose” light
Dark field Microscopy
Light refracted or reflected by specimen
Bright image, dark field
Can see internal structures in live organisms
Good with thin microscope
Phase Contrast
Deviated and undeviated light reaches ocular
Dark field, bright objects with a “halo”
Structures with refractive index different from a cell
Fluorescence Microscopy
Fluorochrome absorbs light then emits light of a different wavelength, filter between specimen and ocular blocks all light except the right wavelength
Only fluorescent tags light up
Fixation
Preserve organism structures, fixed in position, slows them down
Basic Dyes
Bind to negative charges at basic pH
Nucleic acids, surface components of bacteria
-methylene blue, crystal violets, malachite green
Acidic Dyes
Bind to positive charges at acidic pH
-carboxyls, phenolic hydroxyl a
Simple staining procedure
Smear in water Air dry slide Heat fix bacteria Flood slide with stain, time it Rinse off stain Blot dry Done
Used for visualization
Gram Staining
Heat fix smear Stain with crystal violet Iodine (mordant) Decolonize Counter stain
Differentiates between gram + and gram -
Acid fast staining
Heat fix smear
Primary stain penetrates cell wall
Decolonize
Counterstain
