Microscopes

Microscopes

1. Total magnification = Object mag. x Eyepiece mag.

   • Magnification is the degree to which the size of an image is larger than the object itself.

2. Resolution is the degree to which 2 very close objects can be distinguished to see the details.

   • The higher the resolution, the greater the detail of a specimen.

3. LIGHT MICROSCOPES

   • max. resolution is 200nm
   • use objective lenses that can be rotated to view specimens at varying magnifications
   • max. magnification x1500
   • Preparation of Specimens:
     • #1 Staining - chemicals bind to chemicals in/on specimen, allow specimen to be seen - some stains bind to specific cell structures
     • #2 Sectioning - embed specimen in wax, cut sections without damaging their structure
   • can be used to view living organisms
     • relatively cheap, can view natural colour of specimens, small and protable

4. ELECTRON MICROSCOPES

   • Generate a beam of electrons with a wavelength of 0.004nm. Use magnets to direct the beam. Must be viewed on a screen.
   • Can distinguish between objects 0.2nm apart.
   • max. resolution 0.1nm
   • max. magnification x500,000
   • Transmission Electron Microscopes
     • beam passes through thin specimen, pass through less dense areas less easily
     • 2D image
     • x500,000 mag
   • Scanning Electron Microscopes
     • electrons bounce off specimen
     • 3D image
     • x100,000 mag
   • specimen must be placed in a vacuum
     • can only be used by highly trained personnel, only b&w images, can view cell ultrastructure, v. expensive