1. The Microscope

2. Microscope History
Microscopes are instruments which produce a magnified image to help us to examine small objects and their fine details which our eye cannot see.
Microscopes range from simple devices such as a magnifying glass up to high end compound or electron microscopes .

3. Early Microscopes
Simple Microscope
Compound Microscope

4. Microscopes used today
Compound Microscope

5. There are similarities in all microscopes:
Magnify a small object
Separate fine details in order to achieve a high resolution
To render the object against the adjacent background to achieve an acceptable contrast

6. 6

7. Types of Microscopes Simple Dissecting Compound
Scanning Electron Microscope (SEM)
Transmission Electron Microscope (TEM).

8. Using a Microscope to Explore the Cell
Resolution or Resolving power
The ability to distinguish between two objects that are close together
High resolution
Low resolution 8

9. Simple Microscope Similar to a magnifying glass and has only one lens
A lens enlarges an image and bends the light toward your eye.

10. Compound light microscope
Light source: Lamp
Resolution: limited to about 0.2 µm (micrometers)
Magnification: 2000X
2 D image produced
Image seen: In eyepiece
Specimen Preparation: Stain cells on a slide
Type of specimens can be used: Both 10

12. Total Magnification To get the total magnification: Eyepiece Lens X
Objective Lens =
Total Magnification

13. Low Power = 4 x
Medium Power = 10 x
High Power = 40 x

14. Electron Microscope Used to see objects that are smaller than 2µm
There are 2 types of electron microscopes:
Transmission Electron
Scanning Electron

15. Transmission Electron Microscope (TEM)
How it works:
Light Source: Electrons pass through
Resolution: µm
Magnification: 500,000x
Type of image: 2 D
Where image is seen: On a screen/ monitor
Specimen preparation: Very complex
Types that can be used: Dead

16. 16

17. Scanning Electron Microscope (SEM)
How it works:
it passes a narrow beam of electrons over the surface of a specimen.
The specimens must be coated with a very thin film of metal, usually gold.  As electrons bounce off the specimen a television screen picks up the image.
It produces a 3-D image.

19. Light Source: Electrons pass over surface of specimen
How it works:
Light Source: Electrons pass over surface of specimen
Resolution: µm
Magnification: 300,000x
Type of image: 3 D
Where image is seen: On a screen/ monitor
Specimen preparation: Sprayed with gold
Types that can be used: Dead or alive

21. Mitochondria in human liver cell21

22. TEM
SEM
Magnification: 500,000x
Resolution: µm
Magnification: 300,000x
Resolution: µm
*** SEM have lower resolutions than TEM, but they have the advantage of providing 3-D images
Some specially designed SEM’s allow you to observe living specimens

23. How to use a compound microscope
Use the scanning objective (smallest) and bring it into focus using the LARGE KNOB (coarse adjustment)
Switch to low power (medium) and refocus using the LARGE KNOB.   You can re–center the image if necessary.
Switch to high power (biggest) and ONLY focus with the small knob (fine adjustment)
**DO NOT USE THE COARSE ADJUSTMENT ON HIGH POWER – YOU WILL BREAK YOUR SLIDE**

24. Questions 1. Explain how to determine
(a) The highest magnification of a compound light microscope
(b) The diameter of the field of view.
2. How much larger does a grain of sand appear to be under a microscope. if the magnification of the objective lens is 4x and the magnification of the eyepiece lens is 15x?
3 . Read pages in textbook

25. 1. Compound Light Microscope (pg.20)
Consists of 2 lens
Light Source: light (passes through specimen)
Resolution: 200nm or 0.2µm
Magnification: 2000x
Image produced: 2D
Where image is seen: Eyepiece
Specimen Prep: Slicing/staining
Type of Specimen: Dead or alive

26. 2. Transmission Electron Microscope (TEM)
Light Source: electrons (passed through specimen)
Resolution: 0.2nm or µm
Magnification: 500,000x
Image produced: 2D
Where image is seen: Projected on screen/monitor = picture! (internal study)
Specimen Prep: very complex – cross sections
Type of Specimen: Dead

27. 3. Scanning Electron Microscope (SEM)
Light Source: electrons (passed through specimen)
Resolution: 5 nm or µm
Magnification: 300,000x
Image produced: 3D
Where image is seen: Projected on tv screen (study surface of specimen)
Specimen Prep: Sprayed with gold coating
Type of Specimen: Dead or alive