Light and Electron Microscopy

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

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 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. For example: 40X (objective lense) x 10X (ocular lense) = 400X magnification

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

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 Course adjustment Diaphragm Fine adjustment Light Source Base Nice Job !

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

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

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

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

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

References http://education.denniskunkel.com/catalog/product_info.php?products_id=1123 http://micro.magnet.fsu.edu/ http://inventors.about.com/library/inventors/blroberthooke.htm