The Microscope

• Looking at a microscope from the top down, it has twelve basic parts; eyepiece, body tube, nose-piece, objective lenses (2,3 or more), arm, coarse adjustment knob (large knob on the side), fine adjustment knob (small knob on the side), stage, stage clips, aperture (the hole in the stage), diaphragm (adjusts light coming up through the aperture) and the light or mirror.
  
  

Objective Lenses

• A microscope typically has two or more objective lenses with four levels of viewing power; the scanning power at 4X magnification and 40X total magnification; low power at 10X magnification and 100X total magnification; high power at 40 or 43X magnification 400 or 430X total magnification and; oil immersion at 100X magnification and 1000X total magnification.
  
  

Increasing Depth of View

• For depth of view, use the objective lenses attached to the nose-piece. The objectives range in length with the shortest having the least power. Turn the objective lenses so that the scanning, or shortest lens, is over the stage center. Raise the stage or lower the lenses until they are very close to the slide. When viewing a specimen, always center the slide image. Looking through the eyepiece, use the coarse adjustment knob to focus. Center the image again and increase the power by turning to the next objective lens setting. Use the fine adjustment knob to refocus after every increase in power. If you are using a lighted microscope, use the diaphragm to adjust the amount of light coming in through the aperture. Adjusting the flow of light will also aid the depth of viewing at different levels of magnification.
  
  

Using Slides

• Place the specimen on a slide using tweezers. Add a drop of water to the middle of the slide. Place the long edge of the top slide, or slip cover, at the edge of the water drop and let it fall into place; use a toothpick to lay it in place if you like. The water creates a flush viewing surface.
  
  Always raise the lenses or lower the stage before placing the slide to avoid scratching the lenses. Center the slide on the stage. Raise the stage or lower the objective lens until the slide and lens are very close. View through the eyepiece, focusing as needed with the coarse or fine adjustment knobs.
  
  

Immersion Oil

• When you increase depth of viewing to the immersion oil lens, place a drop of immersion oil on top of the slip cover. An average microscope magnifies an image up to 1000X. At this power, the magnification may be impaired with the bending of light. Application of immersion oil on top of the glass slide provides refractive correction.