microscopy

• Magnification = number of times larger the image is in comparison to the actual object.
• Resolution = a microscope's ability to distinguish between 2 objects.
• • Numerical Aperture = a measure of the microscope's ability to gather light and resolve fine details at a fixed distance.
• Illumination = light transmitted through the specimen when viewed
• Focusing = Moving the specimen closer or further away from the objective lens to render a sharp image, controlled by the fine and coarse focusing wheels.
• light microscope

  • The light microscope has the lowest resolution of them all.
  • You can see both living and nonliving specimens in 2D and colour.
  • These are the most readily available. 
  • To view specimens, a stain is used to distinguish between the different structures. 
• Scanning electron microscope

  • The SEM works by passing a beam of electrons over the specimen and scattering.
  • This is then used to render a black and white 3D image.
  • The specimens can only be nonliving
• Transmission electron microscope

  • The TEM works by using a particle beam of electrons to visualise specimens and generate a highly-magnified image.
  • the image is 2D.
  • This has the highest resolution.
• Laser scanning confocal microscope

  • Laser scanning confocal microscopes work by illuminating the specimen with a laser, and using a series of lenses and mirrors to focus the light on a specific area of the specimen.
  • The image produced is 2D
  • can contain select colours.
• Light vs electron microscopes:

  • Light microscopes are inexpensive and lower maintenance
  •  Electron microscopes have a higher resolution.
  • Light microscopes are 2d images and have more colour
  • Both require staining the specimens to see the structures more clearly.
• Cells staining:

  • Light microscope specimens: Gram staining is a common technique used to differentiate two large groups of bacteria based on their different cell walls, either red or violet. Eosin stains the cytoplasm pink. Methylene blue stains the DNA and RNA blue.
  • Electron microscope specimens: most commonly used are uranium, lead or gold because this makes them conductive.