Aim #8: The microscope, an instrument in scientific investigation

1. Aim #8: The microscope, an instrument in scientific investigation • Do Now: If you haven’t handed in the graphing lab, do so now. • Homework: Microscope WS. Rephrase questions in your own words. Do NOT answer the question. Due Tomorrow • Test corrections due Thursday

2. Microscope- Fun Facts • Many people experimented with making microscopes • The first microscope was 6 feet long!!! • The Greeks & Romans used “lenses” to magnify objects over 1000 years ago.

3. 1. 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 Robert Hooke 1635-1703 Anthony van Leeuwenhoek 1632-1723

4. The History The “First” Microscope Zacharias Jansen 1588-1631

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

6. 2.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).

8. 3. The Parts of a Microscope

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

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

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

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

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

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

16. 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

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

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

19. Stage • Supports the slide/specimen Diagram

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

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

22. Base • Supports the microscope Diagram

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

24. 10x x 4x = 40x magnification magnification total of eyepiece lens of obj. lens magnification The specimen being viewed is magnified 40 times. The greater the total magnification, the smaller the field of view (FOV) or area that you see. The lower the total magnification, the larger the field of view (FOV).

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26. 7. 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

27. 7. 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 • Use fine adjustment to focus

28. 8.- 9. What happens to the image AND the field of view as you increase in magnification?

30. HIGH POWER FIELD OF VIEW -How much can you see? In High Power we see 25% of the low power FOV (low power 100 x is 25% of high power 400x) We see less of the specimen but we see more details of the specimen under high power LOW POWER

31. FIELD OF VIEW How do we find the FOV of a microscope? Low Power (100x) Find the diameter of the LP FOV Use the clear metric ruler (mm side) Be sure to line up the first mm mark with the left side of the field. LP FOV = 1.5 mm

32. The mm is too large to measure microscopic objects, so you need to use the micron (micrometer) µm • 1 mm = 1,000 µm • 1 µm = 1/1000 mm or 0.001mm LP FOV = 1500µm

33. So how do we determine how big something is in the microscope? • Let’s see how it works: Use the following formula: FOV # of cells (that can fit across diameter) FOV = 2mm = .5mm # of 4 cells OR .5mm x 1000 =500 microns

35. 10. Magnification vs. Resolution

36. 11. The ability of a microscope to distinguish between two points that are very close to one another (to make objects more clear)

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42. Types of Microscopes • a. compound microscope uses 2 lenses. • b. stereoscope also called a dissection microscope. This has 2 oculars (eye pieces) is used to observe external parts of a specimen.

43. Electron Microscope The limit of resolution restricts the usefulness of light microscopes for studying VERY small specimens such as viruses. • Electron microscopes use a stream of electrons to view these specimens. • Electron microscopes have a limit of resolution more than 1000 times finer than light microscopes.