Microscopy Flashcards
The human eye can distinguish about what micrometer length apart
0.1mm
0.1mm is the size of what cell
human egg cell
describes how many times bigger an image gets when it is put under the microscope
magnification
describes how much fine detail we can see in the image
resolution
defined as the smallest distance that two objects can be apart while still appearing as two objects
resolution
were the first and still most common type of microscope
light microscope
light microscope use what kind of light to create an image
visible light
limit of resolution to 200nm and magnification to x2000
light microscope
use a high power beam of light to create an image
laser scanning microscope
microscope that can show images in 3D
light microscope
has single magnifying lens as the one used by Leeuwenhoek
Simple microscope
has multiple magnifying lenses that uses light as the source of illumination
compound light microscope
who developed the compound light microscope
Hans Jansen
Zacharias Jansen
modern CLM types (4)
bright field microscope
dark field microscope
phase-contrast microscope
flouresence microscope
has a bright background with stained killed specimen or unstained living one
bright field microscope
dark backrgound with unstained living illuminated specimen, used for thin spirochetes like Treponema pallidium
dark field microscope
causes syphiliss
Treponema pallidum
uses the phenomenon of wave interference of light where a special condenser annulus + phase plate are used to cause contsructive and destructive interferences in the light waves passing through structures of different density, this helps in distinguishing cellular structures
phase-contrast microscope
allows viewing of internal structures in living specimen without the need of stains
phase-contrast microscope
uses the phenomenon of florescence (dyes/stains that when excited with UV light emits light of longer wavelength
Flourescence microscope
uses a built in UV light source (not visible light) to view the stained specimens against a dark baground
Flourescence microscope
flouresence stains such as
florescein isothyocynate
IF means
immunoflourescence
used to detect microbes in cells and tissues
Flourescence microscope
Using microscopes to view objects and areas of
objects that cannot be seen with the naked eye
microscopy
You have a specimen consisting of two
lines, and the distance between these two
lines is given as 0.50 μm. If Microscope A
has an LR of 0.45 μm and Microscope B
has an LR of 0.75 μm, under which
microscope(s) can you see the two lines as
separate and distinct?
microscope A
formula for limit of resolution
0.5λ / nsinϴ
where
d = limit of resolution
* λ = wavelength of light used (blue-green)
* n = refractive index of the medium
* ϴ = ½ the angle of the cone of λ entering the
objective
was an English amateur opticist whose discoveries played an important role in perfecting the objective lens system of the microscope
Joseph Jackson Lister
1 micrometer (um) is what to base unit
10^-6m
1 nanometer is what factor to base unit
10^-9
different types of light microscope
simple
compound or complex
light waves and mirrors
light microscope
only 1 lens
magnification ~ 300x
simple microscope
2 sets of lenses
magnification ~ 1000x
compound or complex microscope
a magnifying lens, usually about 10x
eyepiece
focuses the light
condenser
controls the amount of light that enters the objective lens
iris diaphragm
number of lenses that provide different magnifications
objective lense
Electron beams and magnetic fields
- For objects smaller than 0.2 µm in diameter
- In vacuum
electron microscope
types of electron microscope
transmission electron microscope
scanning electron microscope
creates an image by detecting reflected or knocked-off electrons
SEM
uses transmitted electrons (electrons that are passing through the sample) to create an image
TEM
what makes a good microscope
Adequate magnifying power
Provide good contrast
High resolving power
Serves your purpose
microscopic field is
brightly lit
objects under study
are darker
gross morphology
what types of light microscopes
bright field microscopy
microscopic field is dark
objects under study are luminous
dark field micrsocopy
for specimens that are
v invisible in the ordinary LM
v cannot be stained by standard
methods
v distorted by staining
dark field microscopy
shorter wavelength
of light (180nm-400nm)
ü image made visible
by photography or TV
screen
ü detecting substances
(e.g. DNA)
what type of light microscope
UV
ü modification of UV microscope
ü makes use of fluorochromes
ü detection of immunological reactions
flourescence light microscopy
ü Detailed examination of internal
structure
ü Not necessary to fix or stain cells
ü Principle is based on variations in the
refractive indices
phase-contrast microscopy
ü principle is based on variations in the
refractive indices
ü advantage: no diffraction halo
associated with phase contrast
ü disadvantage: the three-dimensional
appearance may not represent reality
differential interference contrast microscopy
ü examine viruses
ü ultrastructure in thin sections of the cells
transmission electron microscope
ü surface features of viruses and
cells
ü reveals a 3-dimensional image
scanning electron microscope
example of EM stains (5)
Osmic acid
Permanganate
Lead
Uranium
Lanthanum
