Compound Microscope: Definition, Parts, Application, Working Principle.

Written by SouravBio · 5 minutes read >

A compound microscope is a class of optical or light microscope. I have already discussed about basics of a microscope on my previous note “Parts of Microscope with their Functions and Working Principle”, you can check them to get an idea about from which class compound microscope belongs and what is a microscope, and more.

Before Jump into it follow my previous note on Microscope. I have also discussed about Simple Microscope in my previous note “Simple Microscope: Working Principle, Uses, Parts, and their Functions” which is also a class of optical microscope.

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Now let’s jump into Our Parent Article;

Definition of a Compound Microscope

  • A compound microscope is a laboratory instrument with high magnification power, which is consists of more than one lenses.
  • Compound Microscopes are used for the study of structural details of a cell, tissue, or organ in sections.
  • A compound microscope can magnify the image of a tiny object up to 1000.
  • The term compound means “multiple” or “complex”.
  • The compound microscopes is consists of two lenses includes, the objective lens (typically 4x, 10x, 40x or 100x) in a rotating nosepiece closer to the specimen, and the eyepiece lens (typically 10x) in the binocular eyepieces.
  • A compound binocular microscope is more commonly used today.
  • Zacharias Jansen created a compound microscope that used collapsing tubes and produced magnifications up to 9X.
  • compound microscopes are generally types of bright field microscope.
  • Compound microscopes may be categorized as an upright microscope, and Inverted microscope.
  • Upright compound microscopes are just like an ordinary microscope which has a lens system, followed by the stage where the specimen is kept, and then the light source.
  • Inverted compound microscopes are exactly the reverse replica of the upright microscope with the illumination system first, followed by the stage, and then the lens system.

Types of Compound Microscope

Classification of Compound Microscope

Compound Microscope is classified in two categories;

A. Light  Microscope

Light Microscope is further classified into four categories such as;

  1. Bright-field Microscope
  2. Dark-Field Microscope.
  3. Phase-contrast Microscope.
  4. Fluorescent Microscope.

B. Electron Microscope

Electron Microscope is further classified into three categories such as;

  1. Scanning Microscope
  2. Transmission Microscope
  3. Confocal Microscope

Working Principle of Compound Microscope

The compound microscopes are works on the principle that when a tiny specimen to be magnified is placed just beyond the focus of its objective lens, a virtual, inverted and highly magnified image of the object are formed at the least distance of distinct vision from the eye held close to the eyepiece.

Mechanism of Compound Microscope

Compound microscopes create an image of specimen by these following steps;

  1. First of all, a specimen is placed between the objective and condenser lens.
  2. The light emitted from the light source is pointed over the specimen with the help of a condenser lens.
  3. After that, the light is passed through the specimen and comes towards the objective lens.
  4. The objective lens captures the light coming from the specimen and creates a magnified image of the specimen, which is called the primary image.
  5. Then the objective lens passed this image through the body tube to the ocular lens or eyepiece and again magnifies the image.
  6. At last, the viewer can see a clear and magnified image of the specimen through the eyepiece.
  7. Occasionally or during the use of a 100x objective lens oil immersion method is used to produce a highly magnified image of the specimen. In this method, a drop of immersion oil is placed between the objective lens and specimen slide.

Magnification Power of Compound Microscope

The total magnification of image formed by the compound microscopes is calculated b this following formula;

m    = D/ fo * L/fe    

Where,   D = Least distance of distinct vision (25 cm)

              L = Length of the microscope tube

              fo = Focal length of the objective lens

              fe = Focal length of the eye-piece lens

Parts of a Compound Microscope

Parts of Compound Microscope
Image: Parts of Compound Microscopes | Image Source: microbiologynote.com
  1. Head:
  • It is located at the top portion of the microscope.
  • It contains Eyepiece.
  1. Eyepiece: 
  • It is also known as ocular, which is located at the top of a microscope. Viewers see the specimen through it.
  1. Body Tube: 
  • It’s a long tube, which connects both eyepiece and objective lenses.
  1. Nosepiece: 
  • Nosepiece is located at the bottom portion of body tube. 
  • Objective lenses are remain attached to it.
  • It can rotate to adjust the objective lens. 
  1. Objective lens: 
  • Compound microscopes contain different types of objective lens (10x, 40x, 100x). 
  • These are located below the nosepiece.
  • These lenses are closest to the specimen.
  1. Stage:
  • The flat metal platform located above the condenser and below the objective lens.
  • The slide of the test specimen is placed over it.
  1. Stage Clips:
  • It is above the stage.
  • It holds the slide.
  1. Base:
  • It supports all the components of the microscope.
  1. Arm:
  • It connects the body tube and base of the microscope.
  1. Illuminator:
  • An illuminator is the light source of compound microscopes.
  • It is a low voltage bulb, which is located below the stage.
  1. Aperture:
  • It is a small hole in the middle of stage.
  • It pass the light from the Illuminator to the specimen slide.
  1. Condenser:
  • It is located below the stage.
  • It gathers and focuses light from the illuminator onto the specimen being viewed.
  1. Iris diaphragm:
  • It adjusts the amount of light that reaches the specimen.
  1. On/off switch:
  • It is located at the base.
  • This switch turns the illuminator off and on.
  1. Stage Controller:
  • These knobs move the stage in left and right or up and down.
  1. Brightness Adjustment:
  • It located at the base.
  • It adjust the brightness of Illuminator.
  1. Diaphragm:
  • It is a five holed disk placed under the stage.

Applications of Compound Microscopes

  1. Compound Microscopes used for blood analysis in pathological labs.
  2. In forensic laboratories, the compound microscopes are used for examining the human cells, paper, etc. Which are related to the crime scene.
  3. Used for the detection of drugs, by viewing their particles under compound microscopes.
  4. In university and college laboratories students use compound microscopes for studying the fungi, bacteria, plant cells, animal cells, etc.

Advantages of Compound Microscopes

  • It is not very expensive.
  • Can look at live samples
  • Can magnify up to 2000 times
  • This microscope is easy to use.
  • These microscopes are easily transferable due to their compact size.
  • It can produce a clear image as compared to a simple microscope.

Disadvantages Compound Microscope

  •  Compound Microscopes Can’t magnify more than 2000 times

Further Reading

Reference

  • https://www.microscopeworld.com/p-3470-what-is-a-compound-microscope.aspx
  • https://www.microscopemaster.com/parts-of-a-compound-microscope.html
  • http://www.madsci.org/posts/archives/1999-01/915771165.Gb.r.html
  • https://sciencestruck.com/compound-microscope-basics-uses
  • https://www.slideshare.net/shrutidhamdhere1/compound-microscope-basic
  • https://en.wikipedia.org/wiki/Optical_microscope
  • https://www.microscopemaster.com/compound-light-microscope.html
  • http://www.funscience.in/study-zone/Physics/OpticalInstruments/CompoundMicroscope.php
  • https://www.biologydiscussion.com/microscope/compound-microscope-structure-and-working-principles/5822

Writer and Founder of Microbiologynote.com. I am from India and my main purpose is to provide you a strong understanding of Microbiology. Microbiologynote.com shares notes related to different branches of microbiology.

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