1. Microscopy

2. Parts of the microscope
Ocular lens
Revolving nosepiece or turret
Arm
Objective lens
Stage
Iris wheel diaphragm
Coarse focus
Light source
Fine focus

3. Using the microscope Change the magnification by
Changing the objective (using the turret) and ocular lenses
Change the focus by
Adjusting coarse and fine focus
Adjust the light or contrast by
Adjusting iris wheel diaphragm (or condenser or mirror if present)

4. Light microscopy Can be used on living cells
Maximum magnification ~ x 2000
Staining can be used to make structures more visible
What can be seen? – cells and organelles

5. Electron microscopy Can not be used on living cells
Maximum magnification x millions
Staining is often used eg silver, gold
What can be seen? – details of organelles, large molecules

6. Staining Stains are used to make some structures more visible
They work by being absorbed by some molecules more than others
Examples include iodine, methylene blue, eosin

7. Working distance
This is the distance between the objective lens and your slide.
The higher the magnification of the lens, the larger the lens
The higher the magnification of the lens, the smaller the working distance

8. What you see under the microscope
Everything is reversed as well as magnified

9. What you see under the microscope 2
If the object appears to be at the top of the slide it is really at the bottom
You need to move the slide away from you
If the object appears to be at the left of the slide it is really at the right
You need to move the slide to the right

10. Diameter of field of view
Distance across centre of field
Measured with a minigrid
Measured in micrometres (m)

11. Using a minigrid Each square is 1 mm by 1 mm in size
The centre grid is further subdivided into 0.1 mm grid squares

12. Millimetres and micrometres
1 mm = 1000 m
1.5 mm = m
0.4 mm = m
2400 m = mm
350 m = mm

13. Millimetres and micrometres
1 mm = 1000 m
1.5 mm = m
0.4 mm = m
2400 m = mm
350 m = mm

14. Magnification and field of view
As magnification increases, field of view decreases by the same factor
x x x400
As magnification decreases, field of view increases by the same factor

15. Calculating field of view when magnification changes 1
magnification x magnification x 400
field of view 4000 m field of view 400 m
Magnification has increased by a factor of 10
Field of view has decreased by a factor of 10

16. Calculating field of view when magnification changes 2
magnification x magnification x 400
field of view 1600 m field of view m
Magnification has decreased by a factor of 4
Field of view has increased by a factor of 4

17. Size of objects under the microscope 1
If given a scale – mm
Measure object with ruler
Measure scale with ruler
Use scale to convert ruler measurement of object to real one
Size = 0.6mm = 600 µm

18. Size of objects under the microscope 1 example
1.7 mm
~1.7 mm
~1200 m

19. Size of objects under the microscope 2
If given a field of view –
Magnification x100, field of view 2000 m
Measure object with ruler
Measure field of view with ruler
Use field of view measurement to convert ruler measurement of object to real one
Size = 1000 m

20. Size of objects under the microscope 2 example
Magnification x40, field of view 4000 m
Cells take up roughly ¼ of field of view
So size of each cell = 1000 m

21. Size of objects under the microscope 3
If given a magnification –
Magnification x 200
Measure object with ruler
Divide size by magnification factor to get real size
Size = 4cm ÷ 200 = 0.02 cm
= 0.2 mm
= 200 m

22. Size of objects under the microscope 3 example
Magnification x100, field of view for x400 = 350 m
Field of view for x100 = 1400 m
Cell is about ½ of field of view = 750m

23. Magnification and field of view
If field of view at x100 is 2000 m, then
Field of view at x400 =
Field of view at x40 =
If field of view at x400 = 250 m, then
Field of view at x100 =

24. Magnification and field of view
If field of view at x100 is 2000 m, then
Field of view at x400 = 2000 ÷ 4 = 500 m
Field of view at x40 = 500 x 10 = 5000 m
If field of view at x400 = 250 m, then
Field of view at x100 = 250 x 4 = 1000 m
Field of view at x40 = 250 x 10 = 2500 m

25. How big are these? 1. Magnification x100, field of view 1600 m

26. How big are these? 1. Magnification x100, field of view 1600 m
~2 fit across field so ~800 m
2. Magnification x400, field of view 200 m
~5 fit across field so ~40 m