VermeerThe Geographer

1
VermeerThe Geographer
So, is The Geographer Leeuenhoek?
2
Relative Sizes
SEM
SEM
both
both
both
both
TEM
TEM
3
Leeuenhoeks Microscope
4
View Through Light Microscope

• Top left View (Elder pith) with Original
  Leeuwenhoek microscope.
• Top right Modern Leitz optical microscope
  (light-ground).
• Bottom Left Modern Leitz optical microscope
  (dark-ground).
• Bottom right Cambridge Stereoscan electron
  microscope image.

5
Light Through Compound Scope
Compound Scope More than One Lens (Advantage
Greater Magnification)
6
What is Resolution?

• The object of microscopy is not just to increase
  magnification, but to do so while retaining
  sufficient resolution.
• Resolution is the ability to see two items as two
  separate things, i.e., two dots as two separate
  dots.
• The resolution a microscope is capable of
  achieving is the smallest distance between two
  dots such that the two dots may be observed
  (resolved) as separate entities.
• In less technical terms, lower resolution means
  an increased degree of fuzziness, i.e., less
  focusable sic? specimens.

7
Electromagnetic Spectrum
8
Wavelength Analogy
9
Light Through Scope
10
Light Interactions
11
Why Care?
12
Immersion Oil
13
Types of Microscopes
14
Bright- vs. Dark-Field (1/3)
15
Bright- vs. Dark-Field (2/3)
This image of the surface of a leaf shows the
differences in contrast between these types of
illumination. Bright-field illumination has very
limited contrast. This image clearly shows that
it is very useful to experiment with contrast
techniques.
Oblique illumination gives a relief-like
enhancement of contrast. In 19th century
microscopes there was often an arrangement for
oblique illumination. Early microscopists knew
that this technique has great advantages!
Dark-field illumination is also one of the most
rewarding techniques. Objects smaller than the
resolving power of the objective can also made
visible simply because they light up! It is
thought that Antony van Leeuwenhoek observed
bacteria using a kind of dark-field illumination!
(see http//www.microscopy-uk.org.uk/mag/artapr02
/dark.html)
16
Bright- vs. Dark-Field (3/3)
Section of Mouse Eye (above)

Hydrodyction the water net
17
Scanning Electron Microscope
18
Transmission Electron Microscope
19
Shadow Casting
20
Freeze Fracturing
21
Staining
22
Gram Staining
Bacillus anthracis
Escherichia coli
23
Acid-Fast Staining
Mycobacterium avium complex (MAC) with acid fast
stain often has the characteristic appearance
shown here with numerous mycobacteria filling
macrophages. Such macrophages may be distributed
diffusely or in clusters.
24
Capsule Staining
25
Link to Next Presentation
26
Numerical Aperture
Need photo of objective lens showing NA,
etc. Need equation showing dependence of
resolution of NA and wavelength.
27
Phase-Contrast Microscopy

28
Fluorescence Microscopy