1. © OCR 2016 Different types of microscopes

2. © OCR 2016 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. © OCR 2016 What is the smallest thing you can see with your eyes? What is the smallest thing you can see with a light microscope?

4. © OCR 2016 Light Microscopes Light rays are focussed using glass lenses to magnify objects up to x1500 Eyepiece lens Objective lenses Coarse and fine Focusing Stage clips Diaphragm Mirror Stage

5. © OCR 2016 Cheek cell plasma membrane nucleuscytoplasm

6. © OCR 2016 Onion cells

7. © OCR 2016 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. © OCR 2016 Electron microscope high voltage electron gun anode condenser lens fluorescent screen projector lens specimen objective aperture lens Intermediate lens Specimen is dead and dehydrated. Black and white image [or false colour]. Objects can be magnified up to x500 000!

9. © OCR 2016 Which parts of this cell would be visible using a light microscope? Nucleus Cytoplasm Cell membrane Possibly mitochondria

10. © OCR 2016 Which parts of the cell would be visible using an transmission electron microscope (TEM) Nucleus Cytoplasm Cell membrane Possibly mitochondria

11. © OCR 2016 What can be seen with an electron Microscope?

12. © OCR 2016 Scanning electron microscope Work in a similar way but are designed to make images of the surfaces of objects.

13. © OCR 2016 Resolution Resolution means how close together 2 objects can be, and still be seen as separate objects. Resolution of a light microscope 0.250 µm Resolution of an electron microscope 0.25 nm Do you know how small µm and nm are?

14. © OCR 2016 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 icroscope – up to x500 000

15. © OCR 2016 Comparing light and electron microscopes Light microscopeElectron microscope Magnification Resolution Type of radiation used Focussed by Type of material that can be viewed Size Preparation and cost of material

16. © OCR 2016 Comparing light and electron microscopes Light microscopeElectron microscope Magnificationx1500X500,000 Resolution250nm0.25nm Type of radiation usedLightElectrons Focussed byGlass lensesElectromagnets Type of material that can be viewed Living/moving/dead/abioticDead/abiotic SizeSmall and portableLarge and static Preparation and cost of material Cheap and easyDifficult and expensive

17. © OCR 2016 How big are cells? Units for measurements mm Micrometers - µm Nanometers – nm 1mm = 1000µm 1µm = 1000nm

18. © OCR 2016 Cheek cell Approximately 60µm in diameter.

19. © OCR 2016 Onion cell Approximately 200µm in length.

20. © OCR 2016 Mitochondrion Approximately 2µm in diameter.

21. © OCR 2016 HIV Virus Approximately 2µm in diameter.

22. © OCR 2016 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. © OCR 2016 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. © OCR 2016 Convert these measurements 1.10mm = µm 2.3mm = µm 3.670 µm = mm 4.0.75mm = µm 5.24 µm = nm 6.186nm = µm

25. © OCR 2016 Convert these measurements - answers 1.10mm =10 000µm 2.3mm = 3 000µm 3.670 µm = 0.67mm 4.0.75mm =750µm 5.24 µm = 24 000nm 6.186nm = 0.186µm

26. © OCR 2016 Quick quiz

27. © OCR 2016 What sort of microscope would you use to… study the internal structure of a mitochondria?

28. © OCR 2016 What sort of microscope would you use to… view sperm cells to see if they are moving?

29. © OCR 2016 What sort of microscope would you use to… look at organisms, cells or tissues that are alive?

30. © OCR 2016 What sort of microscope would you use to… view the surface of a bacterial cell?

31. © OCR 2016 What sort of microscope would you use to… observe the double membrane around a chloroplast?

32. © OCR 2016 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. © OCR 2016 What sort of microscope would you use to… look at a viral cell?

34. © OCR 2016 What sort of microscope would you use to… look at the shape and surface of red blood cells in detail?

35. © OCR 2016 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. © OCR 2016 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.

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