Everything Life Sciences Grade 10

FACT

WARNING:if using
a mirror for
illumination instead
of a light bulb,
never reflect direct
sunlight as you
could damage your
eyes.

8. You can readjust the light source and diaphragm for the clearest image.


9. When changing to the next objective lens use the fine adjustment screw to focus the
   image.WARNING: Never use the coarse adjustment screw for the strongest objec-
   tive lens.


10. Do not touch the glass part of the lenses with your fingers.


11. When finished, move the stage and objective as far away from each other as possible
    and remove the slide.


12. Disconnect the power source and cover the microscope.


13. Carry the microscope by holding it firmly by the ”arm” and ”base” and when walking
    it should be near your chest.

NOTE:

Remember that microscopes are expensive scientific equipment and need to be handled

with care to prevent damaging them. Proper lens paper should be used when cleaning dust

or dirt off any lenses. Avoid getting moisture on the objective lenses. Dust and moisture are

the biggest enemies of microscopes.

Differences between the light microscope and transmission electron microscope

Property Light Microscope Transmission Electron

Microscope

Source Light Beam of electrons

Resolution(how far apart

two objects must be in order

to be distinguished as

separate)

Under optimal conditions

(clean lenses, oil immersion),

the resolution is 0,2

micrometres or 2 thousands

of a millimetre

Resolution of a transmission

electron microscope is about

0,05 nanometres (nm) which

is about 0,5 millionth of a

millimetre. This means that a

transmission electron

microscope has about

10 000 times the resolving

power of a light instrument

Material(alive/ dead) Alive or dead. Bright field or

phase contrast microscopes

enable viewer to observe

living cells. Specimens need

to be stained.

Dead. Electron microscope

images are produced by

passing an electron beam

through tissues stained with

heavy metals.

Example of microscope

image Bacterial spores as seen

under light microscope.

Chlamydomonas reinhardtii,

a single celled green algae,

as seen under the

transmission electron

microscope.

66 3.2. Molecular make up of cells