Microscope: Definition, Parts, Parameters, Types, & Uses

A microscope is an instrument that produces enlarged images of small objects. It provides the observer an exceedingly close view of minute structures at a scale convenient for examination and analysis.

The microscope magnifies microscopic objects that are not visible to the naked eyes. Furthermore, with the help of a microscope, we can see various organisms, like a cell, the structure of dust particles, etc.

What is a Microscope?

The word microscope is derived from the Greek “mikros”, meaning small and “skopein”, meaning to see. Therefore, a microscope is an instrument used for looking at objects that cannot be seen with the naked eye, and microscopy is the science of using a microscope.

A microscope is an instrument that makes an enlarged image of a small object, thus revealing details too small to be seen by the unaided eye. The most familiar kind of microscope is the optical microscope, which uses visible light focused through lenses.

Microscopes are effectively just tubes packed with lenses, curved pieces of glass that bend (or refract) light rays passing through them. The simplest microscope is a magnifying glass made from a single convex lens, which typically magnifies by about \(5 – 10\) times. Microscopes used in schools and professional laboratories are compound microscopes and use at least two lenses to produce a magnified image. There is a lens above the object (called the objective lens) and another lens near your eye (called the eyepiece or ocular lens). Each of these may be made up of a series of different lenses. Most compound microscopes can magnify by \(10,20,40,\) or \(100\) times, though professional ones can magnify \(1000\) times or more. For greater magnification than this, scientists generally use electron microscopes.

Microscope Anatomy

There microscope anatomy includes three structural parts, i.e. head, base, and arm.

Head – This is also known as the body; it carries the optical parts in the upper part of the microscope.

Base – It acts as microscopes support. It also carries microscopic illuminators.

Arms – The microscope arm connects the base and the head and the eyepiece tube to the microscope base. It gives support to the head of the microscope and is also used when carrying the microscope. Some high-quality microscopes have an articulated microscope arm with more than one joint allowing more movement of the microscopic head for better viewing.

The optical parts of the microscope are used to view, magnify, and produce an image from a specimen placed on a slide. These parts include:

Eyepiece – It is situated at the top of the microscope and is also known as the ocular. The part is used to look through the microscope. Its standard magnification is \(10\rm{X},\) with an optional eyepiece having magnification from \(5\rm{X} – 30\rm{X}.\)

Eyepiece Tube – it is the eyepiece holder. It carries the eyepiece just above the objective lens. In some microscopes, such as the binoculars, the eyepiece tube is flexible and rotated for maximum visualization, for variance in the distance. For monocular microscopes, they are none flexible.

Objective lenses – These are the significant lenses used for specimen visualization. They have a magnification power of \(40\rm{X} – 100\rm{X}.\) There are about \(1 – 4\) objective lenses placed on one microscope, in that some are rear facing and others face forward. Each lens has its magnification power.

Nose Piece – also known as the revolving turret. It holds the objective lenses. It is movable; hence, it calves the objective lenses depending on the magnification power of the lens.

The Adjustment Knobs – These are knobs that are used to focus the microscope. There are two types of adjustment knobs, i.e. fine adjustment knobs and coarse adjustment knobs.

Stage – This is the section on which the specimen is placed for viewing. They have stage clips that hold the specimen slides in place. The most common stage is a mechanical stage, which allows the control of the slides by moving the slides using the mechanical knobs on the stage instead of moving it manually.

Aperture – This is a hole on the microscope stage, through which the transmitted light from the source reaches the stage.

Microscopic Illuminator – It serves as a microscope’s light source located at the base. It is used instead of a mirror. It captures light from an external source of a low voltage of about \(100\,\rm{V}.\)

Condenser – These are lenses that are used to collect and focus light from the illuminator into the specimen. They are found under the stage next to the diaphragm of the microscope. They play a major role in ensuring clear, sharp images are produced with a high magnification of \(400\rm{X}\) and above. The higher the magnification of the condenser, the more the image clarity. More sophisticated microscopes come with an Abbe condenser that has a high magnification of about \(1000\rm{X}.\)

Diaphragm –  It is also known as the iris. It is found under the microscope stage, and its primary role is to control the amount of light that reaches the specimen. It is an adjustable apparatus, hence controlling the light intensity and the size of the beam of light that gets to the specimen. For high-quality microscopes, the diaphragm comes attached with an Abbe condenser and combined; they can control the light focus and light intensity that reaches the specimen.

Condenser focus knob – This knob moves the condenser up or down, thus controlling the focus of light on the specimen.

Abbe Condenser – is a specially designed condenser for high-quality microscopes. The condenser is movable and allows very high magnification of above \(400\rm{X}\). High-quality microscopes usually have a high numerical aperture than that objective lenses.

The rack stop controls how far the stages should go, preventing the objective lens from getting too close to the specimen slide, which may damage the specimen. It is responsible for preventing the specimen slide from coming too far up and hit the objective lens.

Microscope Parameters

Two parameters are fundamental in microscopy: magnification and resolution. Both magnification and resolution are essential if you want a clear picture of microscopic objects. For example, suppose a microscope has high magnification but low resolution. In that case, all you will get is a bigger version of a blurry image. 

1. Magnification measures how much larger a microscope (or set of lenses within a microscope) causes an object to appear. For instance, the light microscopes typically used in high schools and colleges magnify up to about \(400\) times the actual size. So, \(1\,{\text{mm}}\) Wide in real life would be \(400\,{\text{mm}}\) wide in the microscope image.
2. The resolution of a microscope or lens is the smallest distance by which two points can be separated and still be distinguished as separate objects. The smaller the value, the higher the resolving power of the microscope and the better the clarity and detail of the image. For example, if two bacterial cells were very close together on a slide, they might look like a single, blurry dot on a microscope with low resolving power. Still, they could be told apart as separate on a microscope with high

What are the Types of Microscopes?

Simple Microscope

The simple microscope is generally considered to be the first microscope. In the \(17{\text{th}}\) century, Antony van Leeuwenhoek created it by combining a convex lens with a holder for specimens. It has a magnifying power between \(200\) and \(300\) times. It was essentially a magnifying glass. A simple microscope presently consists of a magnifying glass with a double convex lens with a short focal length. Examples of this kind of instrument include the hand lens and reading lens. When an object is kept near the lens, then at its principal focus, an image is produced, which is erect and bigger than the original object. The formed image is virtual and cannot be projected on a screen like a real image.

Compound Microscope

A compound microscope is defined as a microscope with a high resolution. It uses two sets of lenses, providing a \(2\)-dimensional image of the sample.
The term compound refers to the usage of more than one lens in the microscope. Also, the compound microscope is one of the types of optical microscopes. The other type of optical microscope is a simple microscope. These devices provide a magnification of \(1,000\) times, which is considered high, although the resolution is low. However, this high magnification allows users to take a close look at objects too small to be seen with the naked eye, including individual cells. Therefore, specimens are usually small and have some degree of transparency. Because compound microscopes are relatively inexpensive, they are used everywhere, from research labs to high school biology classrooms. The difference between a compound and a simple microscope is that a simple microscope uses only one lens, while the compound microscope uses more than one lens.

Stereo Microscope

The stereo microscope, also called a dissecting microscope, provides magnification of up to \(300\) times. These binocular microscopes are used to look at opaque objects or objects that are too large to be viewed with a compound microscope since they do not require a slide preparation. Although their magnification is relatively low, they are still useful. They provide a close-up, \(3 – \rm{D}\) view of the object’s surface textures. They allow the operator to manipulate the object during viewing. Stereo microscopes are used in biological and medical science applications and the electronics industry, such as those who make circuit boards or watches.

Confocal Microscope

Unlike stereo and compound microscopes, which use regular light for image formation, the confocal microscope uses laser light to scan samples that have been dyed. These samples are prepared on slides and inserted; then, with the aid of a dichromatic mirror, the device produces a magnified image on a computer screen. Operators can create \(3 – \rm{D}\) images, as well, by assembling multiple scans. Like the compound microscope, these microscopes offer a high degree of magnification, but their resolution is much better. They are commonly used in cell biology and medical applications.

Scanning Electron Microscope (SEM)

The scanning electron microscope, or SEM, uses electrons rather than light for image formation. Samples are scanned in vacuum or near-vacuum conditions, so they must be specially prepared by first undergoing dehydration and then being coated with a thin layer of a conductive material, such as gold. After the item is prepared and placed in the chamber, the SEM produces a \(3 – \rm{D},\) black-and-white image on a computer screen. Offering great control over the amount of magnification, SEMs are used by researchers in the physical, medical and biological sciences to examine a range of specimens from insects to bones.

Transmission Electron Microscope (TEM)

Like the scanning electron microscope, the transmission electron microscope (TEM) uses electrons in creating a magnified image, and samples are scanned in a vacuum, so they must be specially prepared. Unlike the SEM, the TEM uses a slide preparation to obtain a \(2 – \rm{D}\) view of specimens, so it is more suited for viewing objects with some degree of transparency. As a result, a TEM offers a high degree of magnification and resolution, making it useful in the physical and biological sciences, metallurgy, nanotechnology and forensic analysis.

What are the Uses of Microscope?

The microscope is used in a variety of scientific fields for many different purposes. Whether it be in forensics or traditional medical science, the microscope is an indispensable instrument. However, these are used mainly for:

 Analyzing Tissues

It is common for histologists to study cells and tissues using a microscope. For example, if a section of tissue is taken for analysis, histologists can use a microscope in combination with other tools to determine if the sample is cancerous.

Studying Forensic Data

Evidence collected at a crime scene may contain information that is not visible to the naked eye. For example, striations in bullets can be examined under a microscope to see if they match bullets shot from a particular gun.

To Keep a Check on the Ecosystem

It is common for field biologists to monitor the health of a particular ecosystem, such as a stream, by using microscopes to identify the number and diversity of organisms in a specific region over time.

Exploring Cell Proteins

Research scientists find microscopes an invaluable tool when they study the function of proteins within cells. With today’s technology, many proteins can be labelled with a tag and studied in live cells.

Examining the Structure of an Atom

Powerful microscopes such as atomic force microscopes have aided scientists in studying the surfaces of individual atoms.

Summary

A microscope is an optical instrument used to observe and study tiny (microscopic) objects like even cells. The image of an object is magnified through at least one lens in the microscope. This lens bends light toward the eye and makes an object appear larger than it is. Any microscope consists of three parts: Head (contains the optical parts), base( supports the structure) and arm(connects the head to the base). The eyepiece lens is closer to the observer’s eye.

In comparison, the objective lens, which gives a \(400 – 100\) times magnified image, is closer to the object. The adjustment knobs, aperture, stage, nosepiece, condenser, and diaphragm are important parts of a modern-day microscope that help get a much magnified and resolved image of the object. There are various microscopes, starting from a single lens Simple microscope to a Compound microscope with two lenses; we have various electron microscopes (SEM and TEM) and Light microscopes (confocal). Microscopes have a major role to play when it comes to analyzing tissue or DNA samples or virus strains that help in forensics and biology too. It is with these high powered microscopes that scientists all over the world have differentiated several strains of the COVID-\(19\) virus.

Frequently Asked Questions (FAQs) on Microscope

Q1. What is a simple microscope?
A1: A simple microscope is an instrument that gives an enlarged image of a minute object. It consists of a converging lens of a small focal length. The magnifying glass is a type of simple microscope.

Q.2. What is a microscope?
A2: A microscope is a laboratory instrument used to examine too small objects to be seen by the naked eye, for example, the structure of a cell or to study systems of microorganisms.

Q3: What are types of microscopes?
A3: 1. Simple Microscope
2. Compound Microscope
3. Stereo Microscope
4. Confocal Microscope
5. Scanning Electron Microscope
6. Transmission Electron Microscope

Q4: What are the main parts of a microscope?
A4: The Eyepiece Lens, Eyepiece Tube, Microscope Arm, Microscope Base, Microscope Illuminator, Stage and Stage Clips, Microscope Nosepiece, Objective Lenses, Rack Stop, and Condenser Lens and Diaphragm. 

Q5: What is a compound microscope?
A5: A compound microscope is a high power (high magnification) microscope that uses a compound lens system. A compound microscope has multiple lenses: the objective lens is multiplied by the eyepiece lens to obtain a high magnification.

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