A microscope is a device which allows us to look at very small samples (or objects) by magnifying them to many orders of magnitude. In a simple compound microscope found in school and college laboratories, a light source (known as illuminator) projects the light from the base of the microscope onto the sample. This light passes through an iris diaphragm (or just iris), which is a circular opening that controls the amount of light incident on the sample. This is a manual setting on the compound microscope and is set depending on the transparency of sample, level of contrast needed, etc. This light them passes through a condenser which focuses the light on the sample. We look at the sample through a set of lenses called eyepiece. The light transmitted through the sample enters the microscope through the objective lens and then enters the eyepiece. The magnification offered by the microscope is the product of magnifications of objective and eyepiece.
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