Light Microscope Or Optical Microscope.
Introduction:
The light microscope is an instrument for visualizing the fine detail of an object. It does this by creating a magnified image through the use of a series of glass lenses, which first focus a beam of light onto or through an object, and convex objective lenses to enlarge the image formed.
In 1950 F.H. Janssen & Zacharias Janssen constructed the first simple light microscope. When molecular detail is not required, the light microscope is an ideal, and hence essential instrument for a biologist.
The simplest form of light microscope consists of a single glass lens in combination. All modern light microscope are made up of more than one glass lens in combination.
Principal:
The light microscope operates on the principle that light energy will pass through and around a thin object, such as a microorganism and with the aid of lenses, form a magnified impression on the visual sensory layer of the eye.
The main components of the compound light microscope include a light source that is focused at the specimen by a condensor lens. The source of light is usually the sun or ambient indoor light.
The Optical microscope, also referred to as a light microscope, is a type of microscope that commonly uses visible light and a system of lenses to generate magnified images of small objects.
Optical microscopes are the oldest design of the microscope and were possibly invented in their present compound form in the 17th century.
Basic optical microscopes can be very simple, although many complex design aim to improve resolution and sample contrast.
The object is placed in a stage and may be directly viewed through one or two eyepieces on the microscopes.
In high-power microscopes, both eyepieces typically show the same image, but with a stereo microscope, slightly different images are used to create a 3-D effect.
The sample can be lit in a variety of ways. Transparent objects can be lit from below and solid objects can be lit with light coming through (bright field) or around (dark field) the objective lens.
Polarised light may be used to determine crystal orientation of metallic objects. Phase-contrast imaging can be used to increase image contrast by highlighting small details of differing refractive index.
A range of objective lenses with different magnifications are usually provided mounted on a turret, allowing them to be rotated into place and providing an ability to zoom in.
The maximum magnification power of an optical microscope is typically limited to around 1000x because of the limited resolving power of visible limit
While larger magnifications are possible no additional details of the object are resolved.
Alternatives to optical microscopy which do not use visible light include scanning electron microscopy and transmission electron microscopy and scanning probe microscopy and as a result, can achieve much greater magnifications.
The light microscope is an instrument for visualizing fine detail of an object. It does this by creating a magnified image through the use of a series of glass lenses, which first focus a beam of light onto or through an object, and convex objective lenses to enlarge the image formed.
In the majority of light microscopes, the image is viewed directly through binocular eyepieces that act as a secondary lens in the form of a magnifying glass to observe the projected image.
Light microscopes play an important role in many research laboratories, including electron microscopy facilities.
They can be used as a primary visualization tool or in support of electron microscopy
Working:
Light microscope are compound microscope, which means they contain at least two lenses.
Lenses are curved pieces of glass or plastic that bend rays of light and can magnify objects making them appear bigger than they actually are.
Light microscope shown here magnifies an object in two stages. Light from the mirror is reflected up through the specimen or object to be viewed into the powerful objective lens, which produces the first magnification.
The image produced by the objective lens is than magnified again by the eyepiece lens, which act as a simple magnifying glass.
The magnified image can be seen by looking into the eyepiece lens.
Important Factors in light Microscopy include:
1) Magnification 2) Resolution 3) Contrast
Advantages And Limitations of Light Microscopy:
The light microscope has many advantages over other forms of microscope. Light microscopes are extremely versatile instruments.
They can be used to examine a wide variety of types of specimen, frequently with minimal preparation. Light microscopes can be adapted to examine specimens of any size, whole or sectioned, living or dead, wet or dry, hot or cold, and static or fast-moving.
They offer a wide range of contrast techniques, providing information on the physical, chemical, and biological attributes of specimens. The image from a light microscope is presented in color.
It can be observed with the eye directly, recorded by photographic, video or computer techniques, and image components can be analyzed.
The principal limitation of the light microscope is its resolving power. Using an objective of NA 1.4, and green light of wavelength 500 nm, the resolution limit is ∼0.2 μm. This value may be approximately halved, with some inconvenience, using ultraviolet radiation of shorter wavelengths
References
1. Microbiology by Laning M. Prescott, 5th Edition.
2 .https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/light-microscope#:~:text=Principles,to%20enlarge%20the%20image%20formed
3. https://en.wikipedia.org/wiki/Optical_microscope
4. https://cmrf.research.uiowa.edu/light-microscopy
5. https://www.slideshare.net/gohilsanjay3/light-microscope-109386938
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