Compound Microscope is a type of microscope that is widely used for research and scientific purposes to observe minute objects that are not else visible through our naked eye. Compound Microscope is an incredible tool that helps us to explore the microscopic world in a better way.
Compound Microscope uses two or more lenses to provide a more detailed and magnified image of the sample under observation. Not only it is an extraordinary tool it has a captivating history too. Compound Microscope was developed by a father-son duo Hans Janssen and Zacharias Janssen in the late 1590s, they were the first to use a combination of lenses to create a magnified image of an object. Nowadays it is widely used in various research centers, laboratories, and fields like biology, medicine, etc.
In this article, we will focus on the compound microscope, its components, its usage, and much more. So, Let’s dig more into this but first understand what a microscope is.
What is a Microscope?
A microscope is a device that is used to magnify tiny objects for detailed examination. The word microscope is made up of two words “micro” which means small and “scope” which means to examine or observe. So, a microscope is an equipment used for observing and examining microscopic features of an object (even cells). There are many kinds of microscopes, out of which the most common are a Simple Microscope and a Compound Microscope.
To get more information about microscopes, their types, and their functions, visit Functions of Microscope.
What is a Compound Microscope?
A compound microscope is a device used to magnify an object extensively using a combination of lenses. It uses two sets of lenses for higher magnification and also provides a two-dimensional image of the object. It is another type of optical microscope (the first one being a ‘simple microscope’). It provides an image at high resolution, generally, its optical resolution range is about 40x to 1000x.
A compound microscope provides fine details of the sample under observation. The two lenses used in this microscope are convex lenses with short but different focal lengths. The first lens is called the primary lens (or objective lens) and the other lens is called the ocular lens (or eyepiece lens). The lens above the object is primary and the lens through which we see is the ocular lens.
Diagram of a Compound Microscope
The labeled diagram of the Compound Microscope is added below,
Characteristics of a Compound Microscope
Various characteristics of a Compound Microscope are:
- Compound Microscope provides a higher resolution of about 40x to 1000x.
- Compound Microscope provides a 2-D image of an object.
- Compound Microscope is an optical microscope.
- Compound Microscope is made up of two convex lenses, hence the name Compound Microscope.
- Compound Microscope provides a virtual, inverted, and enlarged image.
Compound Microscope Magnification
The magnification of a compound microscope depends on various aspects and so it varies accordingly. The type of lens used and the number of lenses in a microscope play a major role in its magnification. In a compound microscope, the first magnification of the specimen is done by its objective lens which is further magnified by the ocular lens. Generally, the higher magnification is provided by the objective lens which ranges between 4x to 100x, and the magnification power of the ocular lens falls under the range of 2x to 10x.
To calculate the magnification of a compound microscope, we can simply multiply the magnification of the objective lens with the magnification of the ocular lens. Suppose mo is the magnifying power of the ocular lens and me is the magnifying power of the ocular lens, then
Magnifying power of compound microscope (m) = mo × me
Where,
- mo is the magnifying power of the ocular lens, and
- me is the magnifying power of the ocular lens.
Parts of the Compound Microscope
The compound microscope has a variety of components (or parts). They are divided into two types:
- Structural Components
- Optical Components
Structural Components of Compound Microscope
Some of the most common Structural Components of Compound Microscope are:
- Head: Also known as body. It is the upper part of the microscope that contains the optical components.
- Base: Also known as a foot, it is a U-shaped or a horse-shoe-shaped structure that provides support and stability to the whole structure of the microscope. It is the lowermost part of the microscope.
- Arm: It is a curved shaped structure that is used to grip the microscope while carrying it. It provides a connection between the base and the head of the microscope.
- Pillar: A strong projection beginning from the base and connecting it with the arm is called the pillar of the microscope.
Optical Components of Compound Microscope
Some of the most common Optical Components of Compound Microscope are:
- Stage: It is a rectangular plate positioned at the lower end of the arm with a hole in it, that allows the light to pass through it. The slide or the sample is placed on the stage for observation and examination. It provides stability to the slide using stage clips or mechanical stage clips.
- Body Tube: It is a hollow, tubular structure attached to the upper arm, with one end at the head and the other end at the nosepiece. It provides a pathway between the ocular lens and the objective lens. It has adjustment knobs to shift it up or down.
- Nosepiece: The lower end of the body tube is connected to a circular, rotating metallic part called the nosepiece. It consists of three holes in which the objective lens is embedded.
- Draw Tube: The upper end of the body tube consists of a small fixed tube to hold the ocular lens is called a drawtube.
- Diaphragm: Located beneath the stage, the main role of the diaphragm is to control the light that reaches the sample. It modulates the size and intensity of the light beam with its adjustment knob. Diaphragm is of two types namely: Iris diaphragm and Disc diaphragm.
- Coarse Adjustment Knob: This is the larger knob that is used to adjust the body tube by moving it up or down to bring the sample under examination into direct focus for obtaining a sharp image.
- Fine Adjustment Knob: This is the smaller knob of the apparatus. It is used for obtaining a more defined and sharp image of the sample by providing a more accurate and precise focus on it. It adjusts the focus by moving the body tube at extremely short distances.
- Illuminator: Also known as the light source of the microscope. It usually uses a low-halogen light to provide necessary illumination to the sample under observation. It is located at the base of the microscope and has an adjustment knob to control the intensity of the light.
- Eyepiece Lens: Through this lens, one observes the image of the sample or object under examination. It is also known as an ocular lens. It is located at the top of the body tube and has certain markings on its rim such as 4x, 5x, 10x, 15x, 20x, etc. These markings determine its magnification power.
- Objective Lens: These lenses are located above the nosepiece of the microscope. They are also known as primary lenses as the light emitting through the sample enters through these lenses first and so the initial magnification is done by objective lenses. The image formed by them is real, magnified, and inverted.
- Condenser: It directs and controls the intensity of the light emitting from the illuminator and passing through the sample. It boosts the clarity of the image. It is positioned between the stage and the diaphragm.
- Reflector: It is placed above the base and below the stage. It has two mirrors on either side: a plane mirror(used when light is strong) on one side and a concave mirror(used when light is weak) on the other side. It reflects light rays into the microscope which results in a more clear and sharp image.
Working of Compound Microscope
A compound microscope uses a combination of lenses (the first is the objective lens and the other is the ocular lens) along with a light source for producing a highly magnified image of the sample.
The objective lens produces a real magnified image, which is also the first image of the sample. This image is again magnified by the ocular lens, which provides a more sharp image, this is the final image of the sample. The image produced by the ocular lens is virtual and is observed by the eye through the eyepiece. The light produced by the light sources, enters the eye of the observer by passing through the two lenses, resulting in a highly magnified and bright image, this is the reason the compound microscope is also known as a Bright-field microscope.
Read more about Refraction of Light.
Precautions while using Compound Microscope
While using the compound microscope, the following precautions should be taken:
- Clean the objective lens and ocular lens with a silk cloth and cleaning liquid before use.
- The microscope should be placed upright and should not be tilted.
- The sample under observation should be thinly sliced for proper viewing.
- Place the sample carefully on the slide and fix the slide in position using stage clips.
- While observing the sample, first focus on the low power and then set it up to a high power objective lens.
- While focusing, ensure that the objective lens should not come in contact with the stage or the sample under observation.
- Do not touch the lenses of the microscope.
- Switch off the illuminator after use.
- Clean the microscope after use and keep it back in a safe place.
What is an Optical Compound Microscope?
The word ‘optical’ refers to the use of visible light, hence a compound microscope that uses visible light to illuminate a sample is known as an Optical Compound Microscope. It is also known as a light compound microscope. It also uses a combination of lenses to increase the magnification and resolution of the resultant image of the sample, this includes an objective lens which is placed above the sample, and an ocular lens which is used by the observer to examine the sample. Generally, an optical microscope can provide a magnification up to 1000x or higher. An optical compound microscope can also provide a high resolution of about 0.2 micrometers i.e. it can distinguish between two points that are at least 0.2 micrometers apart.
Simple and Compound Microscope
A Simple Microscope is a microscope that uses a single convex lens, also called a magnifying glass to provide a magnified image of the sample. It produces an erect and enlarged image of the object. In contrast, a Compound Microscope uses multiple lenses to provide a better magnified image of the sample. A compound microscope also consists of some additional features like illumination, adjustable focus, condenser, etc.
The difference between Simple and Compound Microscope is described below:
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It was invented by Anton Van Leeuwenhoek in 1670.
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It was invented by Hans and Zacharias Janssen in the 1590s.
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It uses a single lens only.
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It uses two or more lenses.
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Here, the object is placed within focal length of the lens.
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Here, the object is placed beyond the focal length of the objective lens.
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It can provide a magnification up to 300x.
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It can provide a magnification of up to 1000x or more.
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It uses a concave mirror.
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It has a plane mirror on one side and a concave mirror on the other side.
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It uses natural light as a light source.
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It uses an illuminator which provides light to the object for better examination.
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It does not have a condenser.
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It has a condenser.
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It has only one adjustment knob.
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It consists of a coarse and fine adjustment knob.
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M = 1 + D/F
where F is the focal length of the convex lens and D is the least distance of clear vision.
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m = mo × me
where mo and me are magnification power of the objective lens and ocular lens respectively.
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It is basically used at the school level by students.
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It is widely used for research purposes and in scientific labs.
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Electron vs Compound Microscope
An electron microscope is a high-powered scientific instrument that uses a beam of electrons as a source of illumination. This results in more magnified and higher resolution image as compared to the image formed by a compound microscope which uses a source of light for its illumination. The electrons have a much lesser wavelength than the visible light hence it helps in providing a much finer magnification of the specimen than a compound microscope.
The difference between Electron and compound microscope is given below:
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The first electron microscope was invented by Knoll and Ruska in 1931.
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The first compound microscope was invented by Hans and Zacharias Janssen in the 1590s
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Electromagnetic lenses are used.
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Bi-convex glass lenses are used.
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It uses a beam of electrons as a source of illumination.
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It uses a visible light wave as a source of illumination.
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Its magnifying power can go beyond 200000x.
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It can provide a maximum magnification of about 2000x.
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It can have a resolution of 0.0001μm.
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It can have a resolution of 0.25μm – 0.30μm.
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The black and white colored image is formed.
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Here, the sample can be observed in color.
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Bigger in size, expensive, and need specialized facilities.
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Portable and handy. They are cost-efficient.
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It can be used to observe the specimen at the atomic level. We can observe the surface of the specimen along with its internal structure.
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It cannot be used at the atomic level. We can observe only the surface of the specimen.
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It can only observe dead specimens.
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It can observe both dead and live specimens.
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High-voltage electricity is required.
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High-voltage electricity is not required.
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A vacuum is required.
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There is no need for a vacuum.
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The image is formed at a fluorescent screens.
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Image can be observed by the eye through an ocular lens. No screen is required.
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Used in advanced research and scientific centers only.
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Used in schools, and universities for educational purposes and also used in various research centers.
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Applications of Compound Microscope
Compound Microscope are:
- Used in forensic labs, to examine the human cells and human fingerprints related to the crime scene.
- Used to study live cells as well.
- Used to detect minerals and metals.
- Used for intellectual purposes in schools and universities.
- Used in pathology labs for blood analysis and to detect diseases.
- Used to deeply study micro-organisms like viruses, fungi, plant cells, animal cells, etc.
Merits of Compound Microscope
Compound Microscope have different merits over another kind of microscopes, some of these are:
- Having multiple lenses, provides a more magnified and sharp image of the object.
- It is user-friendly, i.e. easy to use, handle, and carry.
- It has its own illuminator i.e. light source.
- It can be used to observe live samples.
- It is cost-efficient.
- Being compact in size, it provides easy storage.
Demerits of Compound Microscope
Some of the most common disadvantages of Compound Microscope are:
- Its magnification is limited up to a certain extent, the sample can not be viewed after the limit is reached.
- It can be used to observe thin samples only, so light can easily pass through them.
- It cannot be used to study at the atomic level.
Read More,
Compound Microscope – FAQs
1. What is Compound Microscope?
A compound microscope is a microscope that uses a combination of convex lenses to provide a highly magnified 2-D image of the object under observation.
2. Who Invented the Compound Microscope?
Dutch spectacle-maker Hans Janssen and his son Zacharias Janssen invented the compound microscope in the 1590s.
3. What Type of Images are Formed by the Compound Microscope?
In a compound microscope, two images are formed by the two lenses respectively. The first image formed by the objective lens is real, inverted, and enlarged, and then its virtual, inverted, and enlarged image is formed by the ocular lens. Thus, the final image formed by the compound microscope is Virtual, Inverted, and Enlarged.
4. What happens when we decrease the Focal Length of the Objective Lens in the Compound Microscope?
If we decrease the focal length of the objective lens, the magnifying power of the microscope will increase.
5. What is Compound Microscope Formula (For Magnifying Power)?
Magnifying power of compound microscope i.e., m is given by:
m = mo × me
Where,
- mo is the magnifying power of the objective lens, and
- me is the magnifying power of the eyepiece (ocular) lens.
6. How is a Compound Microscope different from a Simple Microscope?
A compound microscope uses a combination of two lenses while a simple microscope uses a single lens only.
7. What is the Principle of Compound Microscope?
The principle of a compound microscope involves using multiple lenses (objective and eyepiece) to magnify an object. It allows for higher magnification and better resolving power than a simple microscope.
8. What is Function of Compound Microscope?
A compound microscope magnifies tiny objects by using multiple lenses (objective and eyepiece) and illuminating them, making them visible for detailed examination. It’s commonly used in laboratories and research.
9. What are the Uses of a Compound Microscope?
A microscope has several uses, a few of them are:
- To examine minute details of cells ( like plant cells, animal cells, etc.)
- To study the internal structure of microorganisms.
- To study atomic structure.
- To analyze tissues.
- To investigate forensic evidence.
- To detect diseases causing microbes such as viruses.
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