1. Unit 4: Cells
Microscopes

2. Objectives: At the end of this lesson, students will be able to:
Identify the parts of the compound light microscope and explain their function.
Calculate the total magnification of a compound light microscope.
Compare and contrast light microscopes and electron microscopes.
Demonstrate how to prepare a wet mount and properly focus a compound light microscope.

3. The Compound Light Microscope
Uses visible light to produce an image.
Specimens must be thin. Why?
Specimens can be alive or dead.
Can magnify objects up to 1000x –

4. Compound Light Microscopes
Compound = “multiple” Light = type of radiation that conveys the image

5. Resolution
the ability of the microscope to make individual components visible
visible light scatters
limits magnification of light microscopes to 1000x

6. The Compound Light Microscope
Four systems
Focusing
Lens
Light
Stage
“Focused Lenses Light the Stage”

7. Calculating Magnification
10x
Total Magnification = Objective x eyepiece magnification magnification

8. Transmission Electron Microscopes
Uses magnets to aim a beam of electrons at thin specimens in a vacuum.
Produces a black & white image based on electron absorption.
Magnify up to 500,000x (practically about 35,000x)
Specimen must be dead and stained with heavy metals.
Transmission Electron Microscope (TEM)

9. How an Electron Microscope Works

10. Transmission Electron Miscroscopy
Sperm flagellum (cross section)

11. Transmission Electron Microscopy
Bacteriophages (viruses that infect bacteria)

12. Transmission Electron Miscroscopy
Human atrial (heart) muscle

13. Scanning Electron Microscope
Can magnify objects up to 1 million times (usually 35,000x)
Specimens can be in gross form. Image is made of the surface of the object.
Electrons are bounced off an object and collected on a photographic plate.
Specimens must also be dry, dead, and stained with heavy metals.
Scanning Electron Microscope (SEM)

14. Scanning Electron Microscopy
Stainless Steel Screen

15. Scanning Electron Miscroscopy
Table Salt

16. Scanning Electron Miscroscopy
Insect on the leg of a daddy long-leg spider

17. Scanning Electron Miscroscopy
Eye of an Ant

18. Scanning Electron Miscroscopy
Spider

19. Other images Human Histology - mostly light microscope images
Dennis Kunkel Microscopy Inc.

20. Compare & Contrast SEM & TEM
From these images include in your notes some similarities & differences between SEM images and TEM images

21. Comparing Microscopes
Light microscopes
Electron microscopes
What is used to make an image?
How does it magnify objects?
How well can it magnify?
What can it magnify?
What can it record?
Beams of electrons emitted in a vacuum
Beams of visible light
Light shines through an object and lenses magnify the image
Electrons are transmitted through or scan the outside of the object.
Usually 35,000 x but can be 1 million x
Up to 1000 x
Specimens must be thin and transparent. Can be living or dead.
Fixed specimens must be dead, dry, and stained with heavy metals.
Full color images.
Can be captured using digital camera or computer
Computer captures digital black & white images that can be colorized.

22. Homework – due January 4, 2012
Read Using a Compound Light Microscope Laboratory.
Answer the Pre-Lab questions on a separate sheet of paper to be handed in at the beginning of laboratory tomorrow.
Goggles and apron are not required tomorrow.

23. Scanning Tunneling Microscope
Uses the charged tip of a probe to get very close to the specimen.
Electrons “tunnel” between the probe and the specimen.
Creates three dimensional computer images of live objects and even atoms.
STM of DNA molecule