Exam 2 Quiz 1 Flashcards
(28 cards)
Two main functions of a microscope
- magnification
- resolution
parfocal
should not have to be adjusted between objective changes
Total magnification =
objective x ocular
resolution
-ability to define two adjacent objects as distinct and separate
-described mathematically by ernst abe in 1870
resolution depends on
- physical properties of light: wavelength
- numerical aperture (Na): light gathering capability of a lens
equation for resolution
R=0.61(wavelength) / NA
how to enhance resolution
-decrease the wavelength of light used
-increase numerical aperture
NA =
nSin theta
n=
refractive index
refractive index of air
1
refractive index of oil
1.5
cone in a 4x
-further from slide, skinnier cone
Dark field microscopy
-opaque light disk tha blocks light so it hits at an angle
-image forms from refractive light only
-used on organisms that are hard to stain (thin, ex. spirochetes)
Phase contrast microscopy
-phase plate where light source has refracted and unrefracted parts
-allows to see unstained organisms
-good for seeing motility, reproduction, and inclusion bodies, sample looks dark and grey
refracted light goes throuh
phase platen
non refracted light goes through
phase ring
Immunofluorescence
-fluorophore attached to sample via antibiotic, can also use GFP tag
-only visibly excited at certain wavelengths and capture emission through the wavelengths
-mercury vapor arc lamp
Confocal microscopy
-concentrate excitation within specific focal point
-add confocal pinhole on microscope
-scans and reads across
-makes a stacked image or Z series to allow for a 3D cell image
Electron scope
-use electrons
-smaller wavelength, higher resolution
-electromagnetic lenses
-vacuum
-dead/dry
-black and white image
Transmission electron scope
-electron source
-condenser lens
-20-100 nm specimen cross section
- 2D image
Scanning electron microscope
-electron hitting the sample and passing through
-collect backscattered and secondary electrons
-3D image but only of surface
-x-ray diffraction for elemental analysis
backscattered electrons
originate on the electron beam
secondary electrons
electrons from atoms within the sample that got kicked out via metal
hanging drop method
-unstained microorganisms
-try to preserve a more natural environment for motility
