Biology

• Microscopy

  The study of cells, cell parts and organisms that are too small to be seen with naked eyes using microscopes
• Light microscope


  • Uses light as a source of radiation to form the image of the specimen being studied
• Electron microscope


  • Uses electron as a source of radiation to form the image of the specimen being studied
• Types of electron microscopes

  • Transmission electron microscope (TEM)
  • Scanning electron microscope (SEM)
• Transmission electron microscope (TEM)


  Electron is passed through the specimen and allows us to see thin sections of the specimen, and thus the inside of the cells
• Scanning electron microscope (SEM)

  Electron beam is passed back and forth over the surface of the specimen, and only the reflected beam is observed to obtain a three dimensional appearance
• How the light microscope works

  1. Substage illumination is the light source

  2. Light must come only from substage position

  3. Iris diaphragm controls the amount of light reaching the specimen

  4. Condenser focuses the light onto the specimen

  5. Objective lens collects the light passing through the specimen and produces a magnified image

  6. Eyepiece lens magnifies the image formed by the objective lens and focuses it onto the eye
• The objective lens is responsible for both the magnification and resolution of the image
• The eyepiece lens magnifies but does not resolve the image formed by the objective lens