Chapter 2
Who is credited with building the first compound microscope?
- Hans Jenson and his son Zacharias - between 1590 - 1595
Who built and used simple microscopes for microbial observation?
- Leeuwenhoek created simple microscopes that could magnify up to 200x-300x
Define Bright Field Microscope and what it is used for
- Light goes through the specimen and objects are viewed against a "bright background"
Define Darkfeild Microscopy and what it is used for
- Light is reflected off the speciment and objects are viewed against a dark background - one of the ways to detect bacteria in syphilis
Define Phase Contrast Microscopy and what it is used for
- Light refracted by living cells is different from light refracted from surrounding medium - Used to observe unstained living organisms
Where are the objective lenses found on a compound light microscope and what would they be used to view?
- Located on the nosepiece and is positioned directly above the specimen.
Explain the difference between a simple and compound microscope.
- Simple Microscope: Have only one magnifying lens Ex. Magnifying lens -Compound Microscope: Have more than one magnifying lens
Define SEM and what it is used for
- The speciment is coated with a metal. The electron beam is scanned, or swept over the specimen. -Typically used to provide a 3-D image of exterior of cells
Define TEM and what it is used for
- Typically uses thin slices of specimens - Used for revealing internal structure of microbial and other cells, view viruses - Resolution is approx -.2 um - Usually not 3-D
Define fluorescence Microscopy and what it is used for
- Uses ultraviolet light instead of white light -UV light excites molecules within the specimen or dye molecules, causing them to glow against a dark background - Used for detection of Myobacterium tuberculosis or Treponema pallidium -Immunofluorescence (labeling antibodies)
Electron microscopes use a beam of ___________ vs. a compound light microscope uses a beam of _______ to view specimens.
- electrons - light waves
Explain what is resolving power or resolution.
Resolving power: the ability of an electronic device to produce images that can be distinguished. Resolution: is the ability to distinguish between two adjacent objects.
What type of microscope is used to view viruses?
-Electron microscopy (EM) -has long been used in the discovery and description of viruses. Organisms smaller than bacteria have been known to exist since the late 19th century (11), but the first EM visualization of a virus came only after the electron microscope was developed.
What is the difference between the ocular vs. objective lenses on a compound light microscope?
-Ocular lens are located in the eye piece. Generally has a magnification of 10x -Objective Lens- Located on the nose piece and is positioned directly above the specifimen. There are four objective lenses (4x, 10x, 40x, 100x)
How do you figure out total magnification on a compound light microscope and give a specific example.
-To get the total magnification take the power of the objective (4X, 10X, 40x) and multiply by the power of the eyepiece, usually 10X. Ex. 10 X 4 = 40x magnification
What type of metric unit is used to describe the size of bacteria? Of viruses?
Bacteria: Micrometer Virus: Nanometer (Micrometer is larger than a nanometer by 1000X)
What is the maximum total magnification of compound light microscope, TEM, and SEM?
Compound Light Microscope: 100x TEM: 500,000 - 1 million X SEM: approx. 50,000 X
What is the resolving power of the human eye, compound light microscope, TEM, and SEM?
Human eye: 0.2 mm or 200 um Compound Light Microscope: approx. 0.2 mm or 200 um, oil immersion lens which is 0.2 um TEM: 0.2 nm SEM: 20 nm
