Basic Parts and Functions of a Compound Microscope

The compound microscope is a popular laboratory instrument in biology. It is used by students to magnify objects that cannot be seen by their naked eyes. The microscope magnifies tiny objects such as bacteria, protozoa, cells and others. Using microscopes is an exciting activity in biology classes because students observe tiny objects and organisms that they have never seen before. The microscope allows them to see moving protozoans in a  sample of pond water. It is also possible to see moving sperms in a sample of semen with the aid of a compound microscope.

It is important for you students to know the basic parts and functions of the compound microscope so that you would be able to use the microscope properly. You would fully enjoy and maximize the uses of a compound microscope if you know how to use each part of it. The vital components of the microscope (the lenses and mirror) are made up of glasses so handle it with care when you’re using it.

Below are the basic parts and functions of compound microscope. Familiarize yourselves with them not just because it is a class requirement but also because it is a valuable knowledge that you could use later in life.

Labeled Parts of a Compound Microscope


Compound Microscope Parts and FunctionsCompound Microscope: Parts and Functions

Eyepiece– This part is where you peep through to look at the magnified object. You can easily recognize this part of the microscope because it is in the top most part of the microscope. It contains a lens with a 10X power of magnification. The lens magnifies a tiny object ten times.

Draw Tube– This part of the microscope connects the objective lenses to the eyepiece. It is attached to the microscope arm for support.

Turret– This is also called revolving nosepiece and directly attached to the draw tube. It is where the objective lenses are attached. As its other name implies, it can be revolved or turned by the user to select what objective lens he/she will use to magnify a particular object.

Arm– This  metal part holds and connects the tube to the base.

Objective Lenses– These are the other lenses used to magnify objects beside from the eyepiece. The objective lenses differ in length; the longest having the highest magnification and the shortest having the lowest . There are 3-4 objective lenses in a microscope and these lenses have different magnification powers (4X, 10X, 40X, and 100X). When the objective lenses are coupled to the eyepiece lens, the total magnification is 40X (4 x 10), 100X, 400X, and 1000X.

Base– This is the bottom part of the microscope and supports the whole device.

Stage– This is the flat platform where you will going to place the slide with the specimen on it. It has a small hole at its center where light from the mirror passes through to illuminate the specimen. The stage has 2 stage clips on it which function in holding the slide in place. If the stage is mechanical, there are knobs connected to the stage clips which you can turn to move the slide from left to right or vice versa.

Mirror– This part is found at the bottom of the stage. It reflects light from an outside source up through the bottom of the stage. The light passes on the whole at the center of the stage and illuminates the specimen. If the microscope is electric, the light source is generated by electricity.

Condenser Lens– This lens functions in focusing the light into the specimen. It gives you a sharper image of the specimen.

Iris diaphragm– This part is attached just below the stage. This is used to vary the size and shape of the light cone projected to the slide. It has a knob which you can move to control the intensity of light projected into your specimen.

Coarse Adjustment Knob– You turn this knob to adjust the distance of the objective lens to the slide and to focus the specimen you are observing. You need to move the objective lens up and down until you can see the magnified image as you peep on  the eyepiece. Be careful not to move the high power objective into the slide too close that you can break it.

Fine Adjustment Knob: This knob is turned to focus the specimen when you are switching from one objective lens to another;  for example,  when you switch from LPO to HPO and vice versa.

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