MIKROSKOP

2. WHAT IS BIOLOGY ???
FROM THE GREEKS
BIOS AND LOGOS
•Bios means human living
•Logos means a knowledge

3. The History
• Hans and Zacharias Janssen of Holland in the 1590’s
created the “first” compound microscope
• Anthony van Leeuwenhoek and Robert Hooke made
improvements by working on the lenses
Anthony van Leeuwenhoek
1632-1723
Robert
Hooke
Hooke
Microscope

4. How a Microscope Works
Convex Lenses
arecurved glass
used to make
microscopes
(and glasses etc.)
Convex Lenses bend
light and focus it in
one spot.

5. How a Microscope Works
Ocular Lens
(Magnifies Image)
Objective Lens
(Gathers Light,
Magnifies
And Focuses
Image
Inside Body
Tube)
Body Tube
(Image Focuses)
•Bending Light: The objective (bottom) convex
lens magnifies and focuses (bends) the image
inside the body tube and the ocular convex (top)
lens of a microscope magnifies it (again).

6. Body Tube
Nose Piece
Objective
Lenses
Stage
Clips
Diaphragm
Light Source
Ocular Lens
Arm
Stage
Coarse Adj.
Fine Adjustment
Base
Skip to Magnification Section

7. Body Tube
• The body tube holds the objective lenses
and the ocular lens at the proper distance
Diagram

8. Nose Piece
• The Nose Piece holds the objective lenses
and can be turned to increase the
magnification
Diagram

9. Objective Lenses
• The Objective Lenses increase magnification
(usually from 10x to 40x)
Diagram

10. Stage Clips
• These 2 clips hold the slide/specimen in
place on the stage.
Diagram

11. Diaphragm
• The Diaphragm controls the amount of light
on the slide/specimen
Turn to let more light in or to
make dimmer.
Diagram

12. Light Source
• Projects light upwards through the
diaphragm, the specimen and the lenses
• Some have lights, others have mirrors where
you must move the mirror to reflect light
Diagram

13. Ocular Lens/Eyepiece
• Magnifies the specimen image
Diagram

14. Arm
• Used to support the microscope when
carried. Holds the body tube, nose piece
and objective lenses
Diagram

15. Stage
• Supports the slide/specimen
Diagram

16. Coarse Adjustment Knob
• Moves the stage up and down (quickly) for
focusing your image
Diagram

17. Fine Adjustment Knob
• This knob moves the stage SLIGHTLY to
sharpen the image
Diagram

18. Base
• Supports the microscope
Diagram

20. Magnification
• To determine your magnification…you just
multiply the ocular lens by the objective lens
• Ocular 10x Objective 40x:10 x 40 = 400
Objective Lens have
their magnification
written on them.
Ocular lenses usually magnifies by 10x
So the object is 400 times “larger”

21. Caring for a Microscope
• Clean only with a soft cloth/tissue
• Make sure it’s on a flat surface
• Don’t bang it
• Carry it with 2 HANDS…one on the arm and
the other on the base

23. Using a Microscope
• Start on the lowest magnification
• Don’t use the coarse adjustment knob on
high magnification…you’ll break the slide!!!
• Place slide on stage and lock clips
• Adjust light source (if it’s a mirror…don’t
stand in front of it!)
• Use fine adjustment to focus

24. Making a microscope slide
Peter Loader @ TLT
1 of 8
The date today is…

25. Aim of the experiment
The aim of the experiment was to make a
microscope slide of an onion skin, look at
it at different magnifications and draw
what we saw. We needed to identify the
cell walls, nucleus and the cytoplasm.
Peter Loader @ TLT
2 of 8

26. Safety
To be safe we wore goggles and
were very careful how we used the
scalpel. Because the glass could
have broken we were very careful
how we held it.
Peter Loader @ TLT
3 of 8

27. Apparatus
In this experiment we used a
microscope, a glass slide, a cover
slip, a pair of forceps and a piece of
onion skin.
Peter Loader @ TLT
4 of 8

28. Method
We cut open an onion and took a piece of very
thin skin. We placed this onto the middle of a
microscope slide.
Then we put a thin piece of glass called a cover
slip on top of the onion skin and gently pressed it
flat.
After that we put the slide under a microscope with
the lens set at low magnification.
Peter Loader @ TLT
5 of 8

29. Method
We turned the focus dial until we could
clearly see the skin. We used a pencil to
draw what we saw and labelled it with the
magnification.
Peter Loader @ TLT
6 of 8

30. Results
This is what we saw.
The higher the magnification we used
the bigger the cells became.
Peter Loader @ TLT
7 of 8
At 20 x
magnification
At 50 x
magnification
At 100 x
magnification
Cell wall
Nucleus
Close up of
onion skin
Cytoplasm

31. Our conclusions
The microscope let us see the onion skin at
different magnifications.
At x 20 magnification it still looked quite far
away but we could see some cells.
At x 50 magnification we could see the cells
clearly.
At x 100 magnification we could see individual
cells, and the cell walls containing the
cytoplasm.
8 of 8 Peter Loader @ TLT

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