1. Microscopes and Basic Measurement
How are they used to study the living environment?

2. Measuring and Units Use a standardized system (metric system)
Meters = length
Gram = mass
Liter = volume

3. Why Use Metric? Base 10 system Easier to convert units
Simply multiply or divide by 10 to change unit

4. Prefixes Used to show smaller or larger measurements Mega Kilo Hecto
Deka
Deci
Centi
Milli
Micro
Nano

6. Important Unit for Microscopes
Micrometers (microns) = µm
1/1000th of a millimeter
1000 micrometers = 1 mm

7. How Big is a Micron?

8. Early Microscopes Anton Van Leeuwenhoek (1670’s)
First to see and describe single celled organisms (protozoa)

10. Robert Hooke (1665)
Coined term “cell”

11. Earliest Microscope?

12. Parts of a Compound Microscope

13. Contain two lenses that cause light rays to bend in such a way to produce an enlarged image.

14. Lenses:
Ocular Lens: eyepiece lens Objective Lens: can be low, medium or high power Look at magnification on lens Lower power is smaller in size

15. Letting in Light:
Mirror or Illuminator: directs light up through the specimen
Diaphragm: regulates amount of light
Disk with different sized “iris” or openings

16. Arm: connects stage and body tube
Stage: platform with opening over which a specimen is placed (clips to hold slide)
Base: supports microscope

17. Eyepiece (ocular): part you look through, holds ocular lens, magnifies 10x
Body tube: connects eyepiece & objective lenses
Nosepiece: holds objective lenses (can be turned)
Objective Lens: magnifies image, can be low, medium, high power

18. Focusing: Coarse Adjustment Knob: use on low power only!!
(never use with high power
you can break your slide!)
Fine Adjustment Knob:
once low power is focused
switch to high power and use
fine adjustment.

19. Magnification How much can you enlarge the image?
Ex: 100x = 100 times as big

20. Finding Total Magnification
Multiply strengths of two lenses you are using.
Ocular lens x Objective lens
Ex:
Ocular = 10x
High Power Objective= 45x
Total Magnification = (10 x 45) = 450x

21. Practice Find Total Magnification: Ocular 2x, Objective 30x =
If Ocular is 10x and Total mag. = 350x
What is the strength of the objective lens?

22. Note:
As you increase magnification you need to let in more light to see your specimen (adjust diaphragm)

23. Resolution How sharp can you get the image?
Ability of microscope to distinguish two objects as being separate (ex: one cell from another)

24. What Happens to Image? Compound Microscopes:
Image becomes inverted and upside down

25. What Happens to Image? When you increase magnification
Object appears larger
Field of view gets smaller

26. Finding Field of View (F.O.V)
Under Low Power: Use millimeter ruler
Ex: 1.5mm
Convert to micrometers
1 mm = 1000 micrometers
So 1.5 mm = 1,500 micrometers
(Move decimal over 3 to right)

27. Finding Field of View (F.O.V)
Under Medium or High Power
Need to set up a proportion
Remember!!
As magnification increases FOV decreases

28. Low power Magnification = High power FOV High power Magnification Low power FOV Ex: 100x = HP FOV 500x 1500 micrometers 500x = HP FOV = 300 micrometers

29. Determining the Size of an Object Under a Microscope

30. View and draw object on low power
Estimate how many objects would fit across diameter of field of view

31. Divide the diameter of FOV by the number of objects that can fit across it.
Ex:
Three letter “e”s fit across FOV of micrometers
Each letter is about 600 micrometers
1800 micrometers = µm
3 letter “e”

32. Comparing Microscopes

33. Compound Light Microscope
Magnification 40x – 1500x
2-D image, inverted, upside down
Uses stains to see details (may kill specimen)
Specimen must be thin to allow light through

34. Dissecting Microscope:
Low mag. 10x – 20x
See true image (right side up)
Specimen can be alive
Can use tools for dissecting specimen
Binocular (two ocular lens) so you can see 3-D image

35. Phase Contrast Microscope:
Uses special filters to show depth without staining.
Can see interior details of living cells

36. Electron Microscopes:
Much higher magnification and resolution than microscopes that use light.
Magnifies up to 200,000x
Uses beam of electrons
Sample placed in vacuum
Cannot view living specimens
Allowed scientists to see structure of cellular organelles