1. The Compound Light Microscope
Compound light microscope – has more than one lens
Blue filter – filters out the long wavelengths of light leaving the shorter wavelengths and improving resolution
Condenser – converges the light beams so they pass thru the specimen
The higher the magnification, the greater the light needed to see the specimen clearly.
Total magnification = ocular mag x obj mag
Parfocal – the specimen remains nearly in focus when changing from one obj to another

2. A comparison of bright-field and dark field microscopy
Bright field: condenser concentrates and transmits light thru the specimen
Dark field: the condenser deflects light rays so that they reflect off the specimen at an angle before they are collected and focused into an image

3. Regular light microscope
Dark-field microscopy:
The background is dark
and the object is bright.
Regular light microscope

4. Phase-Contrast Microscope
Used to study living organisms which would be killed by coloring them with dyes
Accentuates small differences in the refractive index of an organism’s structures
Different refractive indices result in different degrees of brightness

5.                                                       
The Cell Cycle This image sequence shows four different stages during the cell cycle.
The Cell Cycle This image sequence shows four different stages during the cell cycle.

6. Fluorescence Microscopy
Ultraviolet light excites molecules so that they release light of a longer wavelength.
Pseudomonas
fluoresces
naturally.

7. Fluorescent Antibody Staining
Fluorescent dye molecules are attached to antibodies
If the antibody-fluorescent dye-molecules combine with their matching antigen, then the antibody-antigen complex is visible and fluoresces.
Used to diagnose certain illnesses

8. Electron Microscope developed in 1932 uses a beam of electrons
focused by electromagnets
electrons travel in a vacuum tube
Electron micrographs: photos produced from an electron microscope

9. Transmission Electron Microscope
Resolves objects as close as 1 nm
Magnifies up to 500,000 X

10. Specimen Preparation
Specimen is embedded in a block of plastic and cut with a glass or diamond knife to produce very thin slices (sections).
Sections are placed on thin wire grids for viewing so a beam of electrons will pass directly thru the section.
Sections must be thin (70-90 nm). Electrons cannot penetrate far.
Above: Freeze-fracturing –
cell is frozen and fractured with
a knife; the surfaces of the structures become visible

11. Scanning Electron Microscope

12. Scanning Electron Microscope
Creates 3 dimensional views of the surfaces of specimens
Resolves objects as close as 20 nm
Magnifies up to 50,000 X
Specimens coated with a layer of heavy metal such as gold or palladium
Surface scanned by the electron beam
Image displayed on a screen

13. Welcome
to the
Nanoworld

23.                                                                                                                                                           
Fire ant

24.                                                                                   
Butterfly egg