Microscopes Electron
Light
Beams of electrons
Visible light
Radiation
type
Magnification
Radiation
focused by
Typically up to x1000
approx x100,000 in SEM approx X250,000 in TEM
Electromagnets
Lenses usually glass lenses
0.5 nm
200 nm
Resolution
Cells &
Tissues
Not possible to view any living material
Living or dead, can watch living processes
take place
Simpler preparation staining usually
required
Harsher preparation procedures
Specimen
prep
Image
formed by
Image
formed on
Light
Selective absorption of electrons by the specimen.
Human eye can view real image directly by image is formed by projecting focussed image of specimen onto surface
looking into the eyepiece
coated with electron-sensitive compounds
There are advantages and disadvantages to both types of microscopes Compare and contrast the two types outlined here. What
evidence supports a DISADVANTAGE of the transmission electron microscope?
A
The beam of electrons used in the transmission electron microscope often
damage the delicate specimens being observed.
B
The transmission electron microscope magnifies specimens to a much
higher degree than an optical microscope and therefore requires a very
thin specimen
The transmission electron microscope requires that specimens be put
inside a vacuum chamber so the microscope cannot be used to observe
Living specimens
The typical electron microscope can zoom in at only a few discrete levels
and often specimens are best observed at intervals not reached with this
microscope