1. Different types of microscopes
Lesson Element

2. Objectives Learners should be able to:
explain how an electron microscope is different to a light microscope
define the terms magnification and resolution
convert units of measurement used in microscopy
state with examples, when different microscopes are used.

3. What is the smallest thing you can see with your eyes?3
What is the smallest thing you can see with your eyes?
What is the smallest thing you can see with a light microscope?

4. Light Microscopes
Light rays are focussed using glass lenses to magnify objects up to x1500
Eyepiece lens
Coarse and fine Focusing
Objective lenses
Stage clips
Stage
Diaphragm
Mirror

5. Cheek cell
plasma membrane
cytoplasm
nucleus

6. Onion cells

7. To see more detail an electron microscope can be used
Electron microscopes use an electron beam instead of light, which is focussed using electromagnets.
The specimen has to be specially prepared and held inside a vacuum chamber from which the air has been pumped out (because electrons do not travel very far in air).
The image is formed as a photograph (called an electron micrograph) or as an image on a TV screen.

8. Electron microscope Specimen is dead and dehydrated.
high voltage
electron gun
Specimen is dead and dehydrated.
Black and white image [or false colour].
Objects can be magnified up to x !
anode
condenser lens
objective aperture lens
specimen
Intermediate
lens
projector lens
fluorescent screen

9. Which parts of this cell would be visible using a light microscope?
Nucleus
Cytoplasm
Cell membrane
Possibly mitochondria

10. Which parts of the cell would be visible using an transmission electron microscope (TEM)
Nucleus
Cytoplasm
Cell membrane
Possibly mitochondria

11. What can be seen with an electron Microscope?

12. Scanning electron microscope
Work in a similar way but are designed to make images of the surfaces of objects.

13. Resolution
Resolution means how close together 2 objects can be, and still be seen as separate objects.
Resolution of a light microscope µm
Resolution of an electron microscope nm
Do you know how small µm and nm are?

14. Magnification
Magnification is how many times bigger an object is in an image, than in real life.
Magnification using light microscope – up to x1500
Magnification using an electron microscope – up to x

15. Comparing light and electron microscopes
Light microscope
Electron microscope
Magnification
Resolution
Type of radiation used
Focussed by
Type of material that can be viewed
Size
Preparation and cost of material

16. Comparing light and electron microscopes
Light microscope
Electron microscope
Magnification
x1500
X500,000
Resolution
250nm
0.25nm
Type of radiation used
Light
Electrons
Focussed by
Glass lenses
Electromagnets
Type of material that can be viewed
Living/moving/dead/abiotic
Dead/abiotic
Size
Small and portable
Large and static
Preparation and cost of material
Cheap and easy
Difficult and expensive

17. How big are cells? Units for measurements mm Micrometers - µm
Nanometers – nm
1mm = 1000µm
1µm = 1000nm

18. Cheek cell
Approximately 60µm in diameter.

19. Onion cell
Approximately 200µm in length.

20. Mitochondrion
Approximately 2µm in diameter.

21. HIV Virus
Approximately 2µm in diameter.

22. Put these in size order starting with the biggest
Cilia 10µm
Mitochondrion 2µm
Sperm cell 55µm
Ribosome 20nm
Human kidney 13cm
Nerve cell from a giraffes neck 3m
Red blood cell 9µm
HIV virus 100nm
Human egg 100µm

23. Put these in size order starting with the biggest - answers
Nerve cell from a giraffes neck 3m
Human kidney 13cm
Human egg 100µm
Sperm cell 55µm
Cilia 10µm
Red blood cell 9µm
Mitochondrion 2µm
HIV virus 100nm
Ribosome 20nm

24. Convert these measurements
10mm = µm
3mm = µm
670 µm = mm
0.75mm = µm
24 µm = nm
186nm = µm

25. Convert these measurements - answers
10mm = µm
3mm = µm
670 µm = mm
0.75mm = 750µm
24 µm = nm
186nm = µm

26. Quick quiz

27. What sort of microscope would you use to…
study the internal structure of a mitochondria?

28. What sort of microscope would you use to…
view sperm cells to see if they are moving?

29. What sort of microscope would you use to…
look at organisms, cells or tissues that are alive?

30. What sort of microscope would you use to…
view the surface of a bacterial cell?

31. What sort of microscope would you use to…
observe the double membrane around a chloroplast?

32. What sort of microscope would you use to…
look at a cross-section of a sample at high resolution?
What do you think this is a picture of?

33. What sort of microscope would you use to…
look at a viral cell?

34. What sort of microscope would you use to…
look at the shape and surface of red blood cells in detail?

35. What have we learnt using electron microscopes?
Cells contain organelles to carry out different functions.
The internal structure of organelles and how they function.
Structure of bacteria and viruses.
Causes of medical conditions e.g. MS, HIV.

36. Objectives
Can you:
explain how an electron microscope is different to a light microscope
define the terms magnification and resolution
convert units of measurement used in microscopy
state with examples, when different microscopes are used.

37. 37
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