Light microscopy is a well-known tool in research field for identification of small specimen by applying visible light through a string of lenses. The tiny objects can be observed through this technique in the fields of biochemistry, material science, microbiology, pharmaceutical sectors.
Definition of light microscopy
It is a versatile tool to identify, magnify, and observing the small objects by transmitting visible light through a string of lenses. The lenses of this instrument help to focus visible light on the specimen sample for magnifying and producing image of the smaller objects. The sample specimen is generally placed closer to the microscopic lens for perfect analysis.
The magnification form this tool varies due to the existence of different types and number of lenses. The main function of this microscope completely depends on its focus ability of light beam through a sample specimen which should be very small and transparent for generating a perfect image. The generated image can be passed through one or two lenses for further magnification.
History of light microscopy
This microscope was invented by two Dutch scientists namely Hans Janssen and his son Zacharias. They were made this microscope in 16th century by combining lenses in a tube and concluded objects to appear larger and closer. The magnification range of this microscopy was between 3 to 9x.
The simple microscopy was invented Antony Van Lewnehoueek firstly and he could able to observe the presence of various tiny living organisms in pond water like dots. Antony Van Lewnehoueek used a double convex glass lens that was held between two silver plates to construct the simple microscope.
Principle of light microscopy
This microscope generates an optimized image by using a glass lens. The lens ability is very important to magnify and focus the incident light on the sample surface. The incident light radiation bends due to the refraction after transmitted through one medium into another. The refractive indexes of the two mediums that form the interface are used to determine the incident light direction and magnitude of light.
The focul point of lenses focus the light rays at a specific point. The distance from the center of the lens and the focal point is called the focal length. It should be used higher magnification power lenses for properly.
This instrument relates with a factor of resolution. The resolution is the ability of a lens to be able to differentiate smaller specimens that are closely packed together. This resolution property can be determined easily with the help of a numerical aperture of its lens system as well as the wavelength of the light it employs. The wavelength of light is produced during the illuminating of specimen that associates with the numerical aperture.
Types of light microscopy
There are four types of light microscope namely Bright field Light Microscope, Phase Contrast Light Microscope, Dark-Field Light Microscope, and Fluorescence Light Microscope.
The bright field microscope is used very much in schools and colleges. The advanced classroom uses Phase Contrast Light Microscope. Research laboratories uses Dark-Field Light Microscope. Fluorescence Light Microscope is used very much in the fields of clinical, and industrial sectors.
Diagram of a light microscopy
The diagram of a light microscopy is given below:
Parts of a light microscopy
The light microscope has mainly three parts namely mechanical part, magnifying part, and illuminating part. Mechanical part consists of base, c-shaped arm and stage. Magnifying part consists of lens and ocular lens. Illuminating part consists of condenser, iris diaphragm, light source.
The mechanical part is a strong platform where specimen to be viewed is placed. It consists of an aperture at the center for transmitting light to reach the object from the bottom. The specimen object can be moved either sideways or forward and backward.
Magnifying part has the ocular lens which has the magnification of either 10X or 15X. The four types of objective lens are 4X (scanning objective lens contains red color), 10X (Low power objective lens contains yellow color), 40X (High power objective lens contains blue color), and 100X (Oil immersion objective lens contains white color). Theses lenses are attached with the revolving nose piece.
The condenser portion of the illuminating part is located below the stage and made up of a system of convex lenses. It helps to focus light from illuminating sources and can be used to condense light towards the specimen. Iris diaphragm of illuminating part locates below the condenser and operated by small lenses. It controls the light reaching the object.
Light source situated at the base of this device which can be controlled by an ON /OFF switch and a lamp rheostat. Generally, Tungsten-halogen lamps are used very much as the good light sources in this microscope.
There have two types of adjustments knobs in this microscope namely coarse adjustment knob and fine adjustment knob. Coarse adjustment knob is used to move objective lens towards or away from the sample. Fine adjustment knob is used to focus on various parts of the sample.
Functions of a light microscopy
It is an essential tool in the field of industrial and medical research.
It helps to know about the various properties of viruses and bacteria.
It can be identified various diseases in pathology labs to make an easy diagnosis of diseases.
Light microscope is used very much in forensic laboratories to identify human fingerprints.
The soil particles can be analyzed properly by this technique.
The various specimens like fungi and algae can be identified easily by this tool.
The topography of solid sample can be studied properly by this technique.
Tips for using the light microscopy
This microscope should be properly used and handled carefully.
It should carry the C-shaped arm with one hand and other hand under the base.
It should avoid swing the microscope at the time of carrying.
It should cover this microscope with a plastic sheet to protect it from direct light.
It should avoid coarse screw adjustment during the use of oil immersion objective.
It should clean the oil immersion objective with the help of wiping with soft cotton cloth
It should avoid the dry objective to come in contact with oil.
It must be cleaned the lens with paper properly after conducting experiments.
Applications of light microscopy
This microscope is used all over the world in the field of biochemistry and microbiology laboratories to view fixed and live specimens. Light microscope is very essential tool for the identification of basic bacteria cells and parasitic protozoans such as Paramecium. It can be determined the morphological characteristics of living cells such as plant and animal cells with the help of this technique. The bacterial endospores are identified clearly by this tool. It is possible to identify the internal organs of larger cells such as the eukaryotic cells. Bacterial agent like Mycobacterium tuberculosis can be identified easily by applying this technique. Light microscopy is a good identification tool to observe the microorganisms labeled by the fluorochromes and can be differentiate between dead and live bacteria by the color.
Frequently Asked Questions (FAQ’s)
What is light microscopy?
It is a device to illuminate the small specimen by focused light to identification and characterization purposes.
What are the types of light microscopy?
There exist four types of light microscope which are bright field light microscope, phase contrast light microscope, dark-field light microscope, and fluorescence light microscope.
What are the functions of light microscopy?
This microscopic system performs the identification and characterization of various samples in biochemistry and microbiological as well as various research labs.
What are the uses of light microscopy?
This microscopy is used in classrooms, research labs, pathogenic labs, biochemistry labs, genetic labs, forensic labs for identification and characterization purposes of the specimens.
What are the parts of light microscopy?
It has mainly three parts namely mechanical part, magnifying part, and illuminating part. Mechanical part consists of c-shaped arm, base, and stage. Magnifying part consists of objective lens and ocular lens. Illuminating part consists of iris diaphragm, condenser, and light source.
