3.2
The electron microscope
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Learning objectives
 Describe
how electron microscopes
work, compared to light microscopes
 Compare the principles of
transmission and scanning
electroscopy
 Describe the limitations of TEM and
SEM
The principles of microscopy
Radiation from energy source passed through
object, and is focussed to form image on
screen.
 Label diagrams comparing the radiation
pathways in light and electron microscopes
 Complete the table to compare light and
electron microscopy

Difference
Radiation
source
Wavelength
Resolution
Focussing
mechanism
Screen
Light
microscope
Electron
microscope
Difference
Light
microscope
Electron microscope
Radiation
source
light
electron beam
Wavelength
long
short
Resolution
0.2µm
0.1nm (x2000 better
than light microscope)
Focussing
mechanism
convex lenses
electromagnets (repel
negative electrons)
Screen
retina of eye
fluorescent screen
Two types of electron microscope
Images from transmission
electron microscope
What is
different
between the
TEM and the
SEM images?
(ignore colour
enhancement)
Images from scanning
electron microscope
Comparing TEM and SEM
TEM
SEM