1. Light and Electron Microscopy

2. The First Light Microscopes
Around 1590 Zaccharias and Hans Janssen experimented with lenses in a tube, leading to the forerunner of the microscope and the telescope
In the late 1600’s, Anton van Leeuwenhoek was the first to see bacteria, yeast and many other microbes using a microscope

3. How Light Microscopes Work
First, the objective lens gathers light from the specimen and magnifies the image
Most microscopes have several objective lenses that can be rotated into position to provide different levels of magnification (4x, 10x, 40x)
The ocular lens in the eyepiece magnifies and transmits the image to your eye
The magnification of the ocular lens is 10x
For example: 40x (objective lens) x 10x (ocular lens) = 400x magnification
To find the total magnification of the microscope you are using, multiply the magnification of the objective lens by the magnification of the ocular lens.

4. The Parts of a Light Microscope
Light source: Could be a mirror, but most likely it is a bulb built into the base
Diaphragm: Adjusts the amount of light striking an object
Objective lens: Gathers light and magnifies image
Ocular lens (eyepiece): Magnifies objects and focuses light to your eye
Stage: Holds slide
Can be moved using the coarse or fine adjustment knobs to bring the object into focus
Stage clips: Hold slide in place
Base and arm: Structural support for the microscope

5. Can you name the parts? Start on the left side and work from the top down. Then go to the right side and work from the top down.
Ocular lens (eyepiece)
Arm
Objective Lenses
Stage clip
Stage
Coarse adjustment
Diaphragm
Fine adjustment
Light Source
Base
Nice Job !

6. Images Produced by Light Microscopes
Amoeba
Streptococcus bacteria
Anthrax bacteria
Plant cells
Human cheek cells
Yeast cells

7. Beyond Light Microscopes
Light microscopes are limited by their resolution.
Light microscopes cannot produce clear images of objects smaller than 0.2 micrometers
The electron microscope was invented in the 1930’s by Max Knott and Ernst Ruska
Electron microscopes use beams of electrons, rather than light, to produce images
Electron microscopes can view objects as small as the diameter of an atom

9. Types of Electron Microscopes
Transmission electron microscopes (TEMs) pass a beam of electron through a thin specimen
Scanning electron microscopes (SEMs) scan a beam of electrons over the surface of a specimen
Specimens from electron microscopy must be preserved and dehydrated, so living cells cannot be viewed

10. Images Produced by Electron Microscopes
Cyanobacteria
(TEM)
Lactobacillus
(SEM)
Campylobacter
(SEM)
Deinococcus
(SEM)
Avian influenza
virus
House ant
Yeast
Human eyelash

11. Using Microscopes to Visualize the Three Shapes of Bacteria
Cocci (round)
Bacilli (rod)
Spirilla (spiral)
Light microscope:
Three shapes of bacteria
taken with an SEM
Spirilla
Bacilli
Cocci

12. References