Download The Microscope

The Microscope
We use the microscope to
look at objects that are too small
for us to see with the unaided eye.
This is a Compound Microscope
(compound because it uses a
series of lenses rather than only
one), and to use it you must have
care!
When we move a
microscope we always make sure
the chord is wrapped around the
base and we hold it by the arm,
and have our second hand under
the base.
In addition to the terms in
the diagram you should be familiar
with the following:
The eye piece or ocular lens is
located at the top of the
microscope in the tube.
There are also 3 objective lenses that have different magnifications. These are located
on the rotating piece above the stage.
In order to determine the magnification of anything we look at, we need to multiply
the magnification of the ocular lens x the magnification of the objective lens.
For example: If the ocular lens has a magnification of 10x (marked on the lens)
and the magnification of the objective lens is 10x (also marked on it)
Total magnification = 10 x 10
= 100x (the times is added to complete the thought.)
It is imperative that when you start to use the microscope, you start with the lenses as
far away from the sample as possible, and that you start with the lowest
magnification. Once the sample has been placed on the slide, you may use the
coarse-adjustment to bring the sample into focus. To sharpen the image, use the
fine-adjustment. Only after the sample has been put into focus on the lowest
magnification may you rotate the ocular lenses to the next highest magnification. At
this level only use the fine-adjustment knob to bring it into focus. If you do not do as
directed, you will damage your sample and possibly the lens.
Pay attention to all other safety rules outlined to you to make sure you have a
successful experience.
Preparing a Scientific Drawing
Rules:
 Usually a maximum of two drawings per page
 On only one side of page
 Must be large enough to show small details and make sure
they can be labelled
 Shading and stippling (small dots with a sharp pencil), may be
used but only if absolutely necessary (It is better to describe
extra detail in your observations)
 Labels should be in pencil and printed neatly with connecting
lines to the feature. All labels should be on the right-hand
side of the drawing and should be aligned vertically
 Lines to the labels cannot cross each other and cannot have
arrow heads. Try to make them horizontal.
 The title or description should be below the drawing and the
magnification should be indicated at the bottom right of the
drawing.
Magnification = 20x
The Earthworm
Find the magnification of your microscope:
Fill in the table below so that you can calculate the magnification
Eyepiece (ocular lens)
Objective lens
Using the lowest magnification: Mount a piece of
newspaper and look at a letter. Draw its orientation?
What does the microscope do? ___________________
_____________________________________________
_____________________________________________
Magnification
Using a transparent mm ruler, determine how large your field of view is under each
magnification
Lowest Magnification = ________
Medium Magnification = ________
Largest Magnification = _________
Extra: Prepare a slide by dampening the surface of the slide with water using your
finger tip.
Now place with a few grains of salt or a piece of human hair on
the slide. Using the ruler how large do you think it is?
State the magnification and estimated size in mm
________________
_________________
Draw the image in the space provided
Preparing your slide for the onion skin
1. Pull off one section of the onion skin.
Using tweezers or your fingers pull off the
inner skin. (Be very careful not to touch
your face or rub your eyes after touching
the onion – it is an irritant)
2. Place the skin as flat as possible on the
slide (try not to allow any of it to
overlap).
3. Add 1 drop of iodine to the skin. Iodine
is a type of stain so make sure not to
get it on your clothing or skin.
The iodine will colour your skin and
allow you to see more of its features.
4. Place your cover slip on your slide –
your teacher will provide the best
method.
5. Draw the medium and high power
images on a separate sheet of white
paper. Use the instructions for a
scientific drawing and try to match
some of its organelles with those
shown by your teacher.
6. Make sure to hand in your drawing
at the end of class.