Required Practical: Microscopes

• The centre of the microscope has a stage which is where the microscope slide is placed. It has clips to hold the slide in place. Below the stage is a lamp, which has light that passes up through the microscope slide.

  A) Stage

  
• Above the stage of a microscope, we have a set of lenses. These are called the objective lenses and most microscopes have three different ones which usually have a magnification of 4x, 10x, or 40x.

  A) Objective Lenses

  
• At the top of the microscope we have the eyepiece which we use to look through the microscope. It contains the eyepiece lens which has a magnification of 10x.

  A) Eyepiece

  
• The final parts of the microscope are the coarse focussing dial and the fine focussing dial.

  A) Coarse

  B) Fine

  
• How to use an optical microscope to view a prepared slide:

  1. Place slide on stage, use clips to hold slide in place.
  2. Select lowest power objective lens (usually 4x)
  3. Slowly turn coarse focussing dial until objective lens almost touches slide
  4. Look down through the eyepiece
  5. Slowly turn the coarse focussing dial until the cells come into focus
  6. Use the fine focusing dial to bring the cells into a clear focus.
• To calculate the total magnification, we multiply the magnification of the eyepiece lens by the magnification of the objective lens.
• The coarse focussing dial is used to bring the specimen into approximate or near focus. Use the fine focussing dial to sharpen the focus quality of the image after it has been brought into focus with the coarse focussing dial