Saturday, December 9, 2017

Bright-field Microscope


1.      Light microscopy: In this phenomenon, magnification of microscope is obtained by a system of optical lenses using light waves.

a.      Bright-Field Microscopy

The area observed (the microscopic field) is brightly lighted and the objects (Microorganisms) appear dark. Microorganisms appear dark because of the absorption of light by them.
 In general microorganism does not absorb much light. When staining is done, it enhances their ability to absorb light and outcomes in greater contrast and color differentiation.
This kind of microscope generally produces a relevant magnification of about X1000 to X2000.  Magnification greater than X2000, the image becomes fuzzy.
 
Advantages
·         Easy to use.
·         Readily available.
·         Relatively inexpensive.
·         Allows staining reactions to be interpreted.
·         Useful for gross morphological features of bacteria, yeasts, molds, algae and protozoa.

Disadvantages
·         Lack of contrast.
·         Inability to resolve very thin bacteria and viruses.
·         Introduction of artifacts during staining procedures.

( Note: Magnification , Resolving power, limit of resolution, numerical aperture)

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