Characteristics of a Microscope

By John Calhoun

The microscope is one of the most useful scientific tools. Countless scientific innovations have depended on the exponentially greater visibility provided by microscopes. Students around the world learn the principles of microbiology, epidemiology, and chemistry by peering through microscopes.

Eyepiece Lens and Tunnel

The most important part of the microscope is the eyepiece lens. One peers into the lens with one eye, closing the other to focus one's vision on the eyepiece and the magnifying tunnel.


At the bottom of a microscope is the illuminator, a light source that brightens the image of whatever is placed beneath the magnifying lens. Microscopes would not produce such clear magnified images without the light provided by an illuminator.


The stage is the flat, clear, rectangular glass surface on which you place whatever it is you wish to view through a microscope. It is important that the stage be kept clear and clean; otherwise, obstructions or scratches will distort what you observe.

Objective Lenses

Objective lenses are the main magnifying lenses of a microscope. Most microscopes come equipped with a variety of objective lenses that magnify images to different degrees. For example, many microscopes have 4x, 10x, 40x, and 100x lenses.

Diaphragm or Iris

The diaphragm or iris is the part of the microscope that allows you to adjust how much light passes through to the stage. You need more light to observe some substances than others. You must adjust the diaphragm whenever you view something through a microscope. Rarely do two different substances require exactly the same amount of light to pass through an iris.