Microscope

• Microscope


  Instrument used in science laboratories to visualize very minute objects such as cells, microorganisms, producing magnified images with definitive structures
• Microscopes

  • Made up of lenses for magnification, each with their own magnification powers
  • Can view very small specimens and distinguish their structural differences
• Structural parts of a microscope

  • Head
  • Base
  • Arm
• Head

  Also known as the body, it carries the optical parts in the upper part of the microscope
• Base

  Acts as microscope's support, also carries the microscopic illuminators
• Arm

  Part connecting the base and to the head and the eyepiece tube to the base of the microscope, gives support to the head
• Optical parts of a microscope

  • Eyepiece
  • Eyepiece tube
  • Objective lenses
  • Nosepiece
  • Adjustment knobs
  • Stage
  • Aperture
  • Microscopic illuminator
  • Condenser
  • Diaphragm
• Eyepiece

  Also known as the ocular, the part used to look through the microscope, standard magnification is 10x
• Eyepiece tube

  Eyepiece holder, carries the eyepiece just above the objective lens
• Objective lenses


  • Scanner (4x)
  • Low power objectives (10x or 6x)
  • High power objective (45x)
  • Oil immersion objective (100x)
• Nosepiece

  Also known as the revolving turret, holds the objective lenses and can revolve to change magnification
• Adjustment knobs


  • Coarse adjustment knob
  • Fine adjustment knob
• Coarse adjustment knob

  Bigger wheel used to adjust the low power objective in focusing, for rough focusing
• Fine adjustment knob

  Smaller wheel used for delicate focusing with high power and oil immersion objectives, to make the specimen more clear and vivid
• Stage


  Section on which the specimen is placed for viewing, often has mechanical stage to control slide movement
• Aperture


  Hole on the microscope stage, through which the transmitted light from the source reaches the stage
• Microscopic illuminator


  Microscope's light source, located at the base, captures light from an external source
• Condenser


  Lenses used to collect and focus light from the illuminator onto the specimen, play a major role in image clarity
• Diaphragm


  Also known as the iris, adjustable apparatus that controls the amount of light reaching the specimen
• Types of microscopes


  • Light or optical microscopy
  • Electron microscopy
• Light/optical microscopy types


  • Brightfield microscopy
  • Darkfield microscopy
  • Ultraviolet microscopy
  • Fluorescent microscopy
  • Phase contrast microscopy
• Brightfield microscopy


  Most widely used, specimens appear stained or unstained, used for gross morphological features
• Darkfield microscopy


  Uses a special condenser to provide a hollow cone of light, specimen appears bright against dark background, used for living microorganisms
• Ultraviolet microscopy


  Uses ultraviolet light for greater resolution, records image on photographic plate, used to differentiate cellular components
• Fluorescent microscopy


  Specimen treated with fluorescent dye, appears bright and colored under ultraviolet light, used as a diagnostic technique
• Phase contrast microscopy


  Uses special optical system to distinguish materials with slight refractive index differences, used for examining living cells
• Electron microscopy


  Transmission electron microscope uses a beam of electrons, has higher resolving power, used to examine viruses and microbial ultrastructure
• Resolving power


  Ability of the microscope to separate two or more clustered objects so that each can be seen distinctly
• Limit of resolution


  Smallest object that can be seen distinctly, depends on wavelength of light and numerical aperture
• Numerical aperture


  Indication of the light gathering power of the lens
• Magnification


  Ability of the objective lens to render fine details of an object visible
• Total magnification


  Product of the magnification of the ocular and the objective lens
• Focal length


  Distance between the end of the objective and the object when in focus
• Parfocal


  If one objective is in focus, switching to another objective will still maintain the focus
• Immersion oil


  Used to fill the space between the objective lens and slide, has the same refractive index as glass, used for fixed, stained preparations
• Objective lens specifications


  • Focal Length
  • Numerical Aperture
  • Magnification (Objectives)
  • Magnification (Ocular)
  • Total Magnification
• Using and caring for the microscope

  1. Hold the arm with one hand, base with other hand

  2. Place at least 6 inches from table edge

  3. Clean eyepiece, objectives, condenser, mirror with lens paper

  4. Direct mirror towards light source

  5. Start focusing with lowest objective

  6. Check for enough light, adjust mirror and diaphragm

  7. Place slide on stage and clip it

  8. Never tilt if using wet mount or immersion oil

  9. Focus using coarse adjustment, fine adjustment for high power

  10. Clean oil immersion lens with xylene after use