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A Study of the Microscope and its Functions With a Labeled Diagram

Microscope Diagram and Functions
To better understand the structure and function of a microscope, we need to take a look at the labeled microscope diagrams of the compound and electron microscope. These diagrams clearly explain the functioning of the microscopes along with their respective parts.
Debopriya Bose
Last Updated: Mar 26, 2018
Man's curiosity has led to great inventions. The microscope is one of them. Probably, it all started when man, realized that a piece of crystal could magnify images because it is thicker in the center than in the edges. Trials with different pieces of glass and crystals began, and eventually led to the evolution of the microscope. Although Anton van Leeuwenhoek of Holland is known as the father of microscopy, the credit for the earliest working model of the microscope can be given to the Dutch father and son duo, Zacharias Jansen and his son Hans.
Today, the microscope has become an indispensable part of biology. While the compound microscope is most commonly used during our academic tenure, the electron microscope being an advanced model is used in high-end laboratories for carrying out extremely technical and critical research. Here, unlabeled microscope diagrams have been provided for your perusal, which will help you practice and test your understanding of the instrument.
Types of Microscopes
Depending on the source of illumination, microscopes can be divided into two categories. They are:
  • Light Microscopes: These use light rays to illuminate objects. e.g. Dissection microscopes and compound microscopes.
  • Electron Microscopes: These illuminate objects with a beam of highly charged electrons. e.g. Transmission electron microscope (TEM) and scanning electron microscope (SEM). These microscopes provide better magnification than light microscopes.
Compound Microscope Diagram
Compound microscope labeled diagram
The compound microscope uses light for illumination. Some compound microscopes make use of natural light, whereas others have an illuminator attached to the base. The specimen is placed on the stage and observed through different lenses of the microscope, which have varying magnification powers.
Compound Microscope Parts and Functions
Body Tube - It is the part of the microscope that holds the eyepiece.
Arm - The arm connects the body tube to the base. The user must hold this part in order to move the microscope from one place to another.
Base - As the name suggests, the base is the lowest portion on which the whole structure of the microscope rests.
Eyepiece - It is through the eyepiece that we look at the specimen placed on the stage of the microscope. It contains two or more lenses. The most common magnification for the eyepiece is of 10x, however, they can also be of 2x and 5x. An eyepiece is a removable part that can be interchanged with another one of a different magnification.
Objective Lenses - A standard compound microscope contains two primary objective lenses, which can have a magnification of 4x, 5x, 10x, 20x, 40x, 50x, and 100x. The magnification values are written on the side of each lens. The objective turret to which these lenses are attached, can be manually rotated to get the lens to give the desired magnification and focus of the specimen.
Stage - is the platform below the objective lens on which the object or specimen to be viewed is placed. There is a hole in the stage through which light beam passes and illuminates the specimen that is to be viewed.
Stage Clips - There are two stage clips, one on each side of the stage. Once the slide containing the specimen is placed on the stage, the stage clips are used to hold the slide in place.
Diaphragm - is located on the lower surface of the stage. It is used to control the amount of light that reaches the specimen through the hole in the stage.
Illuminator - Simple compound microscopes have a mirror that can be moved to adjust the amount of light that is focused on the specimen. However, some advanced types of compound microscopes have their own light source.
The Adjustments - There are two adjustment knobs, the fine adjustment knob and the coarse adjustment knob. The coarse adjustment knob helps in improving the focus at a low power, whereas the fine adjustment knob helps in adjusting the focus of the lenses with higher magnification.
electron microscope labeled diagram
Electron microscopes focus electron beams upon the specimen instead of using light. This helps to view the specimen at an extremely high resolution. The camera present within the microscope captures images to reveal the finer details of the specimen. This microscope can zoom and view the density of a specimen until it is only a micrometer thick and has a magnification ranging between 1,000 - 250,000x on the fluorescent screen. This microscope needs a computer software to yield precise results.
Electron Microscope Parts and Functions
Electron Gun - The electron gun contains the cathode and control shield or grid. The cathode is the negative electrode through which electrons are generated. These electrons travel as cathode rays or electron beams within the electron microscope. The cathode and the control grid are placed above the electron gun, in a separate compartment away from the lenses. This part must be placed accurately for the microscope to generate accurate results.
Anode - is the second electrode of the electron gun and is shaped like a disk. This disk contains an axial opening for the electron beams to pass through it. A high voltage is made to pass towards the anode, which transmits through it at a constant rate.
Condenser Lens - collects the electron beam, and is responsible for controlling the aperture and focus of the rays. The intensity and diameter of the electron beam is also curtailed and directed through the diaphragm or aperture, onto the specimen and thereafter to the objective lens. The diameter of the beam can be tweaked in order to get the optimal contrast and brightness.
Objective Aperture Lens - is placed beneath the specimen tray. The focal length of this lens is short and ranges from 1-5 mm. The objective lens helps to generate a real image of the specimen, which is magnified further by the intermediate lens along with the projector lens. The concentration of beams and its spatial resolution (ability to view details of the specimen) are dependent on the aperture or diameter of the objective lens.
Intermediate Lens - is actually the first projector lens and is placed above the second projector lens. This magnification is further enlarged through the use of the actual projector lens. The projector lens magnifies the image by five times and thus has a 5:1 ratio or range of magnification. The combination of two lenses allows for greater zooming of the image without having to change the actual length of the electron microscope.
Fluorescent Screen - is a transparent sheet which is coated with a phosphoric substance. The coat is applied on the side of the sheet which is facing towards the rays. When the electron rays hit this sheet, it causes the phosphor to fluoresce or illuminate the image of the specimen. This image is simultaneously captured by the image recording device that is placed beneath the fluorescent screen.
The microscope is an important instrument in the world of biological science. Diagrams have always been of great help in understanding both the structural and functional aspects of entities. These labeled microscope diagrams and the functions of its various parts, attempt to simplify the microscope for you. However, as the saying goes, 'practice makes perfect', here is a blank compound microscope diagram and blank electron microscope diagram to label. Download the diagrams and practice labeling the different parts of these fascinating instruments. All the best!