Microscope

• Microscope


  An instrument used to see very small objects that cannot be seen with the naked eye
• Robert Hooke published "Micrographia"


  1665
• Robert Hooke's observations using a microscope


  • Razor blades aren't that sharp
  • Insects have strange compound eyes
  • Plants appear to be made of tiny structures called cells
• Antonie Van Leeuwenhoek


  • Designed his own microscopes to better examine the quality of fabrics
  • Later examined many other subjects and eventually discovered microorganisms
  • Described seeing tiny creatures (in pond water, beer, saliva, and semen) that he called animalcules
• Light or Optical Microscopes


  • Their lenses bend normal visible light in order to function
  • Can be used to see cells and many other microorganisms
  • Not powerful enough to see most viruses, atoms, and molecules
• Electron Microscope


  • Shoots electrons at their subjects instead of photons (shot by light microscopes)
  • Viruses can be examined (pollen, HIV, Ebola, COVID, etc.)
• Electron Microscopes

  • Transmission Electron Microscope (TEM)
  • Scanning Electron Microscope (SEM)
• Transmission Electron Microscope (TEM)


  Tend to be most ideal for visualizing structures within a specimen (internal structures)
• Scanning Electron Microscope (SEM)


  Tend to be most ideal for visualizing the 3D surface
• Scanning Probe Microscope (SPM)

  • Sees by feeling the bumps and valleys along the surface of an object with a tiny metal probe
  • Data collected as it scans is used to generate an extremely high-resolution image
  • Atoms can be examined
• Parts of a compound microscope

  • Eyepiece (Lens) or Ocular Lens
  • Eyepiece Tube (Body Tube)
  • Revolving Nosepiece
  • Objective Lenses
  • Arm
  • Stage
  • Stage Clips
  • Diaphragm
  • Coarse Focus
  • Fine Focus
  • Stage Controls or Knobs
  • Condenser (Lens)
  • Illuminator or Light Source
  • Base
• Eyepiece (Lens) or Ocular Lens


  Where you look through and it magnifies the image of the specimen (10X)
• Objective Lenses

  • Microscopes have 3-4 that revolve on the nosepiece
  • Scanning Objective Lens (4X)
  • Low Power Objective Lens (10X)
  • High Power Objective Lens (40X)
• Total magnification


  = 10X (Eyepiece Lens) x 4X/10X/40X (Objective Lenses)
• Diaphragm


  • Controls the amount of light passing through the slide
  • Located below the stage and is usually controlled by a round dial
• Coarse Focus


  Moves the stage to provide a general focus on the specimen
• Fine Focus


  Moves the stage in smaller increments to provide a clear view of the specimen
• Condenser (Lens)


  Focuses the light onto the specimen
• Illuminator or Light Source

  • Most light microscopes use a low-voltage bulb which supplies light through the stage and onto the specimen
  • Mirrors are sometimes used instead
• Brightfield Light Microscopes

  Typically produce a darker image on a light background
• Brightfield Light Microscopes

  • Mostly used in academic settings
• Darkfield Light Microscopes

  • Has a piece that blocks the light source (light stop)
  • Most light has been blocked so the only light visible is light reflected or refracted from structures within the specimen
  • Produces light images in a dark background
• Other Types of Light Microscopes

  • Phase-contrast
  • Differential Interference Contrast
  • Fluorescence
  • Confocal
  • Two-photon