1. The Microscope

2. Basic information
Microscopes are devices that produce magnified images of structures that are too small to see with the unaided eye
Two types of microscopes:
Light microscopes
Electron microscopes

3. Light microscopes The first type of microscope
Works by passing visible light through a specimen
Can magnify objects only about 1000 times (1000X)

4. Compound light microscope
Used at NOHS – uses two lenses to form the image

5. Compound Light Microscope

6. Magnification Eyepiece: 10X Three objectives: Total magnification
Low: 4X
Medium: 10X
High: 40X
Total magnification
Eyepiece x objective lens

7. Light microscope
Magnification: number of times larger the image appears than the object actually is
Resolving power: the clarity of the object
An optical device is limited by its resolving power
Light microscopes cannot show the details of the cell’s internal structure.

8. Electron Microscope Uses a beam of electrons instead of light
Developed in 1950s to view smaller objects
Can only be used to view dead and preserved cells
No color
Expensive
Has a higher resolving power than the light microscope
Can magnify about 100,000 times

9. Scanning electron microscope
Used to study the detailed architecture of cell surfaces
SEM composes images on a TV screen from the electrons that bounce off the surfaces of the object.
SEM images are usually about 10,000 to 20,000 times larger than life size.
Useful for showing organisms and cellular surfaces under high magnification
Can produce three-dimensional images

10. Scanning electron microscope

11. Transmission electron microscope
Used to study the details of internal cell structure
Composes images on camera film
Images are usually 100, ,000 times larger than life size
Useful for showing the internal structure of cells

12. Transmission electron microscope

13. Main problem
Electron microscopes cannot be used to study living specimens because the specimen must be held in a vacuum chamber—all air and liquid must be removed.
We still use the light microscope for studying living cells.

14. Parts of the Microscope
Eyepiece: contains the magnifying lens
Arm supports the body tube
Fine adjustment knob sharpens the image
Coarse adjustment knob brings the image into a rough focus
Base supports the microscope
Diaphragm regulates the amount of light passing up toward the eyepiece
Low power objective is the shortest lens (4X)
High power objective is the longest (40X)
Nosepiece holds the objectives

15. Parts of the microscope

16. Scientists to Remember
Anton van Leeuwenhoek: first to use a simple microscope to study nature
Robert Hooke: used a light microscope to look at cork; called small chambers in cork “cells”

17. Using the microscope
Always carry the microscope with one hand on the arm and one hand on the base
Always begin your study with the low power objective in place
Only use the coarse adjustment knob with the low power objective
Only clean the lens of the microscope with clean lens tissue.
When you finish using the microscope you should always remove the slide and store the microscope with the low power objective in place