1. Tools of the Biologist
Microscopes

2. Compound Light Microscope

3. Light illuminated (uses visible light)
Light passes through the specimen → through the objective→ bounces off a mirror→ into your eye
Creates a two dimensional image

4. Parts of a Compound Light Microscope

5. Handout
Reference page: xxxviii

6. Calculating Magnification
Magnification: how much an image is enlarged under a microscope
The numbers found on the eyepiece and the objective that are marked with an X tell you how many times the lens of each microscope part magnifies an object

7. Ex. If the eyepiece magnification is 10X and the low power magnification is 10X, then the total magnification under the low-power objective is 100X.

8. Our microscopes all have an eyepiece magnification of 10X
We have 3 objectives with magnifications of 4X, 10X, and 40X
What are the total magnifications of each?

9. 10X x 4X = (scanning objective)
10X x 10X = (low-power objective)
10X x 40X = (high-power objective)

10. Some compound light microscopes have a total magnification of 1000X
These use an oil immersion objective

11. Light Demand
The high power objective needs the most light to magnify the object/ specimen

12. Field of View
Field of View: the area that you see when you look into a microscope
Which objective has the largest field size (allows you to see the most total area)?
Low power objective has the largest field size

13. Field of View

14. Depth of Focus
Depth of Focus: the thickness of the plane of focus (dimensions)
With a greater depth of focus, you can focus on more of your object without it being partially blurry and see more detail
Low power has the greatest depth of focus

15. What does this mean?
Under low power, you can see more detail in multiple planes

17. Depth of Focus (lowest mag)

18. Viewing Slides
When you move the slide to the right, the image moves left
When you move the slide to the left, the image moves right
When you move the slide up, the image moves down
When you move the slide down, the image moves up

19. Microscope Use
Carry the microscope by grasping the arm with one hand and placing the other under the base
Place the microscope on the table with the arm towards you

20. Use the low-power objective first
Switch to higher power objects as needed
If you switch to high-power, adjust only the fine adjustment knob

21. Adjust the diaphragm to change the amount of available light as needed

22. Stereoscopes

23. Stereoscope Also called a dissecting microscope Light illuminated
Creates a 3-D image

24. It has a lower magnification than the compound light microscope (cannot see specimens at the cellular level)
Our stereoscopes have a 10X eyepiece magnification and 1X and 3X objective magnification

25. Magnifies opaque objects
Has two light sources—one above the stage, the other below the stage

26. Poppy Seeds as Seen with an Unaided Eye

27. Poppy Seeds Under a Stereoscope

28. Electron Microscope

29. Electron Microscopes (SEM) Scanning Electron Microscope:
Bounces electrons off of an object
Uses magnets to focus the image

30. Displays an image on a screen
Provides a 3-D image
Allows us to see images too small to view through a compound light microscope

31. What’s This?

32. Spider Image with a SEM

34. Housefly’s Foot

36. Cat’s Flea

37. Electron Microscope Cont.
Transmission Electron Microscope:
Electrons pass through a specimen
Image is focused with magnets

38. Image is displayed on a screen
Creates a 2-D image
Used to reveal internal structures

39. MRI of a Rat’s T-Cells (Immune Cells)