The coarse focus knob is the larger of the two focus knobs. It is used for large scale movements raising or lowering the stage, typically used for smaller values of objective lens magnification, like 4x or 10x.

- ocular lens (eye piece)   
- rotating objective lenses  
- coarse focus knob  
- fine focus knob  
- stage  
- illuminator   
- condenser  
- diaphragm  
- mechanical stage 
- x/y mechanical stage knobs  
- rheostat

Parts of a Microscope

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The ocular lenses are where you look through when viewing a specimen. They typically have magnification of 10x and can either be monocular or binocular (as pictured). 

Ocular Lens (Eye Piece)

Rotating objective lenses allow the change in magnification based which of the three rotating lenses is focused on the specimen. Each of the lenses has varying magnification, often ranging from 4x to 100x.

Rotating Objective Lenses

Coarse Focus Knob 

The fine focus knob is the smaller of the two focus knobs. It is used for smaller movements of raising and lower the stage, typically used with higher objective magnification, like 40x or 100x.

Fine Focus Knob

The stage is the platform that secures and holds the slide in place for viewing the specimen.

Stage 

The illuminator is the high-intensity light source on the bottom of the microscope, shedding light up onto the stage.

Illuminator

The condenser is a lens that converges the light rays coming from the illuminator, focusing the light on the stage.

Condenser

The diaphragm is a piece in the condenser that can be open or closed depending on the desired amount of light being projected onto the stage. 

Diaphragm 

The mechanical stage allows the stage to move left/right or forwards/backward in order to view different areas of the specimen in focus. It is moved using the X/Y knobs

Mechanical Stage (X/Y Knobs) 

The rheostat acts as another mechanism of controlling brightness because it is a dimmer switch that control brightness intensity coming from the illuminator.

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