THE MICROSCOPE

• Microscope


  Used to magnify (i.e., visually enlarge) objects too small to be visualized w/ the naked eye

  
• Microscope in 1600s


  • Consisted of one lens (magnified 100 times)
• Microscope today


  • Uses two lenses (ocular (10x) and objective)

  
• Types of microscopes


  • Bright field
  • Phase contrast
  • Fluorescent
  • Dark field
  • Electron (Transmission and Scanning)

  
• Bright field microscope


  Visible light passes through a series of lenses
• Total magnification


  Ocular x Objective
• Key components of a microscope

  • Magnification
  • Resolution
  • Contrast

  
• Light microscope


  Uses natural or artificial light, condenser and diaphragm to regulate intensity and angle of illumination
• Focusing


  • Low Power Objective (LPO)(10x) - 16mm working distance
  • High Power Objective (HPO)(40x) - 4mm working distance
  • Oil Immersion Objective (OIO)(100x) - 1.8mm working distance
• Locating and focusing an object

  1. Adjust light source with LPO

  2. Make certain the diaphragm is open

  3. Move the tube downward using the coarse adjustment knob

  4. Look into the ocular and reverse the motion with the coarse adjustment

  5. When swinging the high and dry objectives into position

  6. When swinging into OIO, place small drop of cedar oil on the portion of the slide to be examined

  7. To focus using OIO the fine adjustment must be moved very slowly
• Parfocal


  Images remain focused when objectives are changed
• Spherical aberration

  Lack of uniform focus (OIO). The slight turn of the fine adjustment knob, the periphery of the field may clear. With another adjustment, the center is in focus
• Other types of microscopes

  • Phase contrast
  • Fluorescent
  • Dark field
  • Electron (Transmission and Scanning)
  • Compound
• Phase contrast microscope


  • Advantage - observation of viable microorganism
• Electron microscope


  • Can magnify up to 1,000,000x

  
• Compound microscope


  • Can magnify up to 1000x