FEATURE

LIGHT MICROSCOPE

ELECTRON MICROSCOPE

Part of electromagnetic spectrum used

Visible light
760nm (red) – 390nm (blue)

Electrons
app. 4nm

Maximum resolving power

app. 200nm

0.2nm

Maximum magnification

x1000 – x1500

x500 000

Radiation source

Tungsten or quartz halogen lamp

High voltage (50kV) tungsten lamp

Lenses

Glass

Magnets

Interior

Air-filled

Vacuum

Focussing screen

Human eye (retina), photographic film

fluorescent (TV) screen,

photographic film

Preparation of specimens

Temporary mounts living or dead

Tissues must be dehydrated. Water vapour destroys vacuum
So tissues must be dead

Fixation

Alcohol

OsO₄ or KmnO₄

Embedding

Wax

Resin

Sectioning

Hand or microtome
slices ≤ 20 000nm
Whole cells visible.

Microtome only.
Slices ≤ 50nm

Stains

Water soluble dyes e.g. methylene blue, iodine solution

Heavy metals e.g. Pb & U salts

Support

Glass slide

Copper grid