Microscopy: Principle & It’s Types

What Is Microscopy

The world microscopy originated from the Greek “mikros”, which means small and “skopein” meaning to see. The microscope is an instrument that is used to view a sample or object which can not see with the unaided eyes. Microscopy is the science of using a microscope. Microscopy refers to magnifying (enlarging) a small object, sample or bacteria or physical characteristics of cracks and grain boundaries at the molecular level.

History

The origin of the microscope dates back to around 1000 AD when a glass share was used to enlarge the object. In 1021 Iqbal al Haytham has written a book on “Optics” to a better understanding of the behaviour of light. Therefore it was not clear until 1590 that Hans and Zacharia Janssen placed a lense in a tube to create the forerunner of the modern microscope. In 1609, Galileo developed a new microscope that was a compound microscope.

Ernst Abbe developed a formula that could calculate the maximum resolution of the microscope. In 1931, Ruske and Knoll made the first Transmission electron Microscope, For this, he used an idea from Swaziland. From the 20th century to the beginning of the 21 st century, innovation continued in all areas of the microscope.

Types Of microscopy

There are two types of fundamental microscopy:

1. Light Microscope
2. Electron Microscope

Light Microscope

The light microscope is also known as an Optical microscope. A light microscope uses a series of glass lenses to focus light to create an image. A light microscope resolves the image with the help of light. They use lenses to focus on the object to magnify it and produce an image. The magnification of the microscope varies depending on the type and number of lenses that make up the microscope.

On the basis of the number of lenses there are two types of microscopes:

Simple light microscope: It uses a single lens and has low magnification.

Compound light microscope: It uses at least two sets of the lense, an objective lens and an eyepiece, It has high magnification power.

The function of the light microscope depends on the capability to focus a beam of light through a small, transparent specimen to produce an image. The transparent specimens allow easy and quick penetration of light.

Principles:

Optical microscopes use a glass lens to view an image, and magnification is determined by the ability of the lense to bend and focus light onto the sample that forms the image. When a ray passes through one medium and enters the other, it bends at the interface and causes refraction. The curvature of light is determined by the index of refraction, which indicates how slowly a substance slows the speed of light. The direction and extent of the bend of light are determined by the index of the refraction of the two media forming the interface.

Types Of Light Microscope:

These are the types of the light microscopes:

1. Bright Field Microscope: In this type of microscopy the microscopy field appears as Bright light whereas microorganism appears as light due to the absorbance of light.
2. Dark Field Microscope: In this type of microscope the field appears dark and microorganism or objects appears brightly illuminated.
3. Phase Contrast Microscope: This technique is based on the fact that the light passes through one material and enters into another material with a slightly different index of refraction or thickness and undergoes a phase change.
4. Fluorescence Microscope: In this microscope specimen itself works as a light source. Fluorescent dye is used on the stained specimens to study.

Electron Microscopy

Electron microscopes are scientific instruments that use a highly energetic beam of light to study fine objects. It is a technique for obtaining high-resolution images of objects. It is used in biomedical research to examine the reveal the ultrastructure of tissue, cells and organelles. Electron Microscopy examination can provide the following information about objects:

• The Surface features of the objects direct the relationship between these features and materials properties.
• The shape and size of the which makes the object.
• The element and compound of the object through which the object is made up of.
• It also provides the crystallographic of the object i.e how the atoms are arranged in the object.

Types Of Electron Microscope

1. Transmission Electron Microscope (TEM): Transmission Electron Microscope uses a beam of light to focus the specimen to produce a highly magnified and detailed image of the specimen.
2. Scanning Electron Microscope (SEM): In this microscope electron that is reflected back from the specimen is collected, and the surface of the specimen is imaged.

References: 

www.microbiologynotes.org

www.umassmed.edu