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The Mirror to be exact and the Diaphragm specifically the Iris and Disc Diaphragm
it is also known as the iris. It is located above the light source.
Iris diaphragm
The diaphragm regulates the amount of light that reaches the objective lens. It is also called the iris.
Too much light overwhelms the eye's ability to distinguish contrast and therefore detail in the specimen. Microscopes therefore have the ability to reduce the amount of light impinging on the specimen using a diaphragm, rather like the iris of the eye does.
Equipped on the Condenser of the microscope, the iris diaphragm is a shutter controlled by a lever that is used to regulate the amount of light entering the lens system.
function of iris diaphragm
The Diaphragm of the microscope regulates the amount of light shown.
The iris diaphragm adjusts the amount of light allowed in.
The iris diaphragm controls the amount of light passing through the slide or specimen, while the substage condenser focuses a cone of light on the slice or specimen.
The iris diaphragm controls the amount of light passing through the slide or specimen, while the substage condenser focuses a cone of light on the slice or specimen.
The iris diaphragm controls the amount of light passing through the slide or specimen, while the substage condenser focuses a cone of light on the slice or specimen.
The Iris diaphragm in the condenser. (the lever sticking out just above the "8" in the image above.
The radial and circular muscles of the iris.
This iris diaphragm of a microscope contains the amount of light that can enter through to the specimen. If the condenser iris diaphragm is open, the image will be bright; if it is closed, it will be dim.
The condenser and iris diaphragm.
The diaphragm reduces the light from under the stage which can improve the image contrast.