Oil Immersion Microscope: Operating Guide

The presence of oil between the objective and the specimen decreases the diffraction of light that as it passes through the objective and this is important for resolution of objects at 1000X (100X objective and 10X eye piece). To use the 100X objective, also called the oil immersion objective, follow the instructions given above and:

  • Place a drop of immersion oil on the slide in the viewing area.
  • Turn the revolving nosepiece to engage the oil immersion objective.
  • Use the fine adjustment control to focus the image.

The oil on the specimen must be free of bubbles or the image is impaired. To remove bubbles, slightly move the oil immersion lens back and forth over the specimen.

It is very important that all oil be cleaned off the lens before storing the microscope.

Oil Immersion Microscope Operating Guide


  • Question
  • Answer

How does using immersion oil change the numerical aperture?

The numerical aperture is a measure of the cone of light that can be gathered by the objective and therefore a decrease in light that is diffracted will increase the light that is gathered by the objective.


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