1. MICROSCOPES As tools for the biologist

2. How are microscopes useful? They are used to extend human vision by making enlarged images of objects. They are used to study organisms, cells, cell parts, and molecules. Yeast cells

3. Light Microscopes Typically used to see small organisms and cells Compound light microscopes shine light through a specimen and uses two lenses to magnify the image

4. Four Main Parts of the Microscope Eyepiece:Eyepiece: magnifies the image (usually 10X) Objective Lenses:Objective Lenses: enlarge the image of the specimen from 2X to 100X Stage:Stage: platform that supports the slide Light Source:Light Source: provides the light for viewing the object

5. Magnification and Resolution Magnification: Magnification: the increase of an object’s apparent size Multiply the magnification of the ocular lens with the objective to get the total magnification Resolution: Resolution: is the power to show details clearly in an image Light microscopes are only useful up to 2000X Onion cells at 100X magnification

6. Scanning Electron Microscopy Passes a beam of electrons over the specimen’s surface, providing a 3D view Spray the surface with a fine metal coating, the electron beam causes these to emit a shower of electrons Projects this image onto a fluorescent or photographic screen Magnifies up to 100,000X and you can look at living things Pollen Grains Open chamber of an SEM

7. Transmission Electron Microscope Emits a beam of electrons through a very thinly sliced specimen Magnetic lenses enlarge the image and focus it on a screen or photographic plate These can magnify objects up to 200,000 times Can only see dead things Polio virus TEM

8. Scanning Tunneling Electron Microscope Looks at surfaces at the atomic level Can see things at the nanometer scale (1,000,000,000X) Can be used from near 0 K to a few hundred degrees Celsius!! Image of surface reconstruction on a clean Gold (Au(100)) surface, as visualized using scanning tunneling microscopy. The individual atoms composing the material are visible. Surface reconstruction causes the surface atoms to deviate from the bulk crystal structure, and arrange in columns several atoms wide with regularly-spaced pits between them.