Bresser NATIONAL GEOGRAPHIC 90-39001 Instrucciones De Uso página 13

7. Condition and prepare viewed objects
7.1. Condition
With the Barlow lens nearly fully extended, your microscope's magnification can
be doubled. Both transparent and non-transparent specimens can be examined
with this microscope, which features both direct and transmitted light. If opaque
specimens are being examined, such as small animals, plant parts, tissues, stones
and the like, the light is reflected from the specimen, through the lens and eye-
piece, where it is magnified, to the eye (reflected light principle, switch position
I). If opaque specimens are being examined, the light from below goes through
the specimen, lens and eyepiece to the eye and is magnified en route (direct light
principle, switch position II).
Some small water organisms, plant parts and animal components are transparent
by nature, but many others require pretreatment — that is, you need to make a thin-
nest possible slice of the object by hand cutting or using a microtome, and then
examine this sample.
7.2. Creation of thin preparation cuts
Specimens should be sliced as thin as possible. A little wax or paraffin is needed to
achieve the best results. Put the wax into a heat-safe bowl and heat it over a flame
until the wax is melted. You can use a candle flame to melt the wax.
DANGER!
Be exremely carfeful when dealing with hot wax, as there is a danger
of being burned.
Then, dip the specimen several times in the liquid wax. Allow the wax that encases
the specimen to harden. Use a MicroCut (22) or other small knife or scalpel to
make very thin slices of the object in its wax casing.
DANGER!
Be extremely careful when using the MicroCut, knife or scalpel.
These instruments are very sharp and pose a risk of injury.
Place the slices on a glass slide and cover them with another slide before attempt-
ing to view them with the microscope.
7.3. Creation of your own preparation
Put the object to be observed on a glass slide and cover the object with a drop of
distilled water (No. 3) using the pipette (No. 3, 20a).
Set a cover glass (available at a well-stocked hobby shop) perpendicular to the
edge of the water drop, so that the water runs along the edge of the cover glass
(No. 4). Now lower now the cover glass slowly over the water drop.
TIP: The gum medium (23b) supplied is used to make permanent
i
slide cultures. Add it instead of distilled water. The gum medium
hardens so that the specimen is permanently affixed to its slide.
8. Experiments
Now that you're familiar with your microscope's functions and how to prepare
slides, you can complete the following experiments and observe the results under
your microscope.
8.1. Newspaper print
Objects:
1. A small piece of paper from a newspaper with parts of a picture and some
letters
2. A similar piece of paper from an illustrated magazine:
Use your microscope at the lowest magnification and make a slide preparation
from each object. Place the slide with the newspaper on the microscope table and
observe the slide. The letters in the newspaper appear broken because the news-
paper is printed on raw, inferior paper. Now observe the slide with the magazine
preparation. Letters of the magazine appear smoother and more complete. The
picture from the newspaper consists of many small points, which appear somewhat
dirty. The pixels (raster points) of the magazine image appear sharper.
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