Parts of a Compound Microscope


To study the parts of a compound microscope. 



Compound microscope 

A compound microscope is a high-resolution, multi-lens device used to view and magnify objects not visible to the human eye. It uses two sets of lenses providing a 2-dimensional image of the sample.  

  • Objective lens – The primary lens has a magnification capacity of 4X, 10X, 40X, or 100X, is positioned close to the object, and forms an inverted image with apparent magnification. 
  • Eyepiece or Ocular lens – The secondary lens or ocular lens is at the top to view the observed image.  

Parts of a compound microscope 

The parts of a compound microscope can be categorized into: 

  • Mechanical components - Including head, eyepiece tube, arm, stage, stage clips, nosepiece, condenser, focus knobs (coarse and fine adjustments), and base. 
  • Illumination Components - Including illuminator.  
  • Optical components - Including eyepiece (ocular lens), objective lens, diaphragm.  

Mechanical components 

Head and eyepiece tube: The upper part of the head attached to the eyepiece tube supports optical components, maintains lens alignment, and supports the eyepiece tube for optimal performance. 

Base and arm: The base and arm of the microscope provide stability and facilitate the connection of the base and upper parts, ensuring easy handling and transportation. 

Stage and clips: The stage is a flat platform attached to the arm with an adjustable height. The clips help to hold the slides, and the center hole passes the light to the object. 

Condenser: It is located under the stage and is positioned between the stage and the diaphragm. It regulates the light intensity that passes from the illuminator to the hole.  

Nosepiece: It is a circular; rotating metal part positioned at the bottom of the body and holds three different objective lenses. 

Focusing knobs (coarse and fine adjustments): The coarse adjustment knob adjusts for general focus by moving the body tube up whereas the fine adjustment is used for clear visualization.  

Optical components 

Eyepiece (ocular lens): The eyepiece at the top of the body tube visualizes the magnified image by objective lenses to the closest view. 

Objective lens: It is located at the top of the stage, magnifies and projects the magnified image of the specimen which can be observed through the eyepiece. 

  • Oil immersion objective (100X) - Ideal for maximum magnification to observe fine details, and enhance resolution, and clarity of the structure of bacteria or cellular components. 
  • High power objective (45X) - Ideal for detailed examination of specific specimen features after initial scanning.  
  • Low power objective (10X) – Ideal for initial observation and location, also offering a wide field view and frequent scanning of the entire specimen. 

Diaphragm: The diaphragm, located below the stage controls the amount of light reaching the specimen.  It is of two types: disc and iris.  

Illumination components 

Illuminator: It is the light source, either a mirror or light used to illuminate the object to the eyepiece. 

Significance of compound microscope 

  • Magnification power allows to magnify the image clearly for a comprehensive analysis of the sample, yielding detailed information.  
  • User-friendly and easy to operate.  
  • Versatile application plays a major role in biology, medicine, and all material sciences for detailed study.  
  • Research assistance supports the study of new discoveries, providing enhanced visualization and strengthening research efforts. 

Limitations of compound microscope 

  • Limited resolution: It has the limited capacity to display extremely fine details, particularly when using very high magnification. 
  • Sample preparation: Prior to examining under a compound microscope, many specimens require special preparation. 
  • Potential damage to specimens: Delicate specimens can be harmed if not handled carefully while being prepared for viewing under a compound microscope. 

Uses of compound microscope  

  • Useful for learning about microorganisms and their functions, including cell division and cellular processes.  
  • Assists in analyzing studies of leaves, stems, roots, and reproductive organs to learn plant anatomy and physiology.  
  • Facilitates to understanding the structure of microorganisms using permanent slides and samples obtained from the environment.  



  • Eyepieces must be cleaned using a silk cloth and cleaning liquid before use.  
  • Avoid tilting while working or using the microscope. 
  • Start focusing the specimen from the lower magnification and then to the higher.  
  • Avoid objective lenses hitting the stage while focusing. 
  • For well–mount preparation, a coverslip must be used before observing.  
  • Ensure the immersion oil is applied before focusing on higher magnification.  


Learning outcomes 

Student understands,   

  • The concept of compound microscope.  
  • The various parts and working mechanism of the compound microscope. 
  • The significance, limitations, and uses of the compound microscope.