microscopy

• The first microscope was 6 feet long
• The Greeks & Romans used "lenses" to magnify objects over 1000 years ago
• Hans and Zacharias Janssen of Holland in the 1590's created the "first" compound microscope
• Antoni van Leeuwenhoek and Robert Hooke made improvements by working on the lenses
• Robert Hooke observed a mass of tiny cavities from thin slices of cork with his self-made microscope
• Antoni van Leeuwenhoek observed protozoa, red blood cells, capillary systems, and the life cycles of insects
• Robert Brown observed plant cells with a distinct central part (nucleus) and described the streaming movement of the cytoplasm
• Dujardin observed that cells were filled with thick, jelly-like fluids (protoplasm)
• Matthias Schleiden concluded that plants are composed of cells and formulated the cell theory
• Rudolf Virchow concluded that all cells must come only from pre-existing cells
• Theodore Schwann stated that cells are the elementary particles of both plants and animals and formulated the cell theory
• Max Knoll and Ernst Ruska built the first transmission electron microscope
• James Watson and Francis Crick discovered the structure of DNA
• Microscopes produce an enlarged image of an object
• Resolution is the ability of a microscope to show two very close points separately
• Magnification increases the apparent size of an object
• To calculate the power of magnification, multiply the power of the ocular lens by the power of the objective
• Compound Light Microscopes:

  • Specimen mounted on a glass slide must be thinly sliced or very small
  • Can be used to study LIVE specimens
  • Highest Maximum magnification is around 1000X
• Dissecting microscopes/stereo microscopes:

  • Useful for looking at large specimens and doing dissections
• Electron Microscope:

  • Transmission EM (TEM) uses a beam of electrons to produce an enlarged image of very thinly sliced specimen
  • Scanning EM (SEM) provides a 3D image and specimens are not sliced for viewing
  • Cannot be used to view living specimens
• Body Tube holds the objective lenses and the ocular lens at the proper distance
• Revolving Nosepiece holds the objective lenses and can be turned to increase the magnification
• Diaphragm controls the amount of light on the slide/specimen
• Light Source projects light upwards through the diaphragm, the specimen, and the lenses
• Ocular Lens magnifies the specimen image
• Arm supports the microscope when carried and holds the body tube, nosepiece, and objective lenses
• Stage supports the specimen slide and moves it in different directions
• Coarse Adjustment Knob moves the stage up and down quickly for focusing
• Fine Adjustment Knob moves the stage slightly to sharpen the image
• Base supports the weight of the microscope
• The image is inverted and reversed when viewed through a microscope
• Total magnification is determined by multiplying the power of the ocular lens by the power of the objective
• Higher magnification results in a smaller field of view
• Convex Lenses are used to make microscopes and bend light to focus it in one spot
• Field of view is the diameter of the area visible through the microscope