Bright Field Microscope
Types Of Light Microscopes
A light microscope is a biology laboratory instrument or tool, that uses visible light to detect and magnify very small objects and enlarge them.
They use lenses to focus light on the specimen, magnifying it thus producing an image. The specimen is normally placed close to the microscopic lens
Microbiologists currently employ a variety of light microscopes in their work; bright-field, phase contrast, dark-field and fluorescence microscopes are most commonly used.
Modern microscopes are all compound microscopes, that is the magnified image formed by the objective lens is further enlarged by one or more additional lenses.
Light Microscopy in which magnification is obtained by a system of optical lenses using light waves.
Types Of Light Microscope:
Bright Field Microscope:
In bright field microscope, the specimen appears as dark against the bright background. Bright field microscope is widely used microscope in laboratories and it also known as Compound or Light Microscope.
Staoned, fixed and live specimens are observed under a bright field microscope. A broght field microscope is consist of a piece of apparatus, Consisting of an eyepiece, an objective lens, stage and light source, which collects electromagnetic radiation in the visible range.
Principal:
The specimen to be observed is placed on the stage of a bright field microscope. The light will transmit through the specimen from the source and then it will enter the objective lens where a magnified image of specimen will form.
Then the light will enter an ocular lens or eyepiece, where the image will furthur magnify a then enter into the observers eyes. The viewers observe a dark image against a bright background.
In a bright field microscope, only the scattered light are able to enter the objective lens and transmitted lights or unscattered lights rays are emmited, that's why the viewer see a dark image against the bright field.
Path Of Light:
A stained specimen or sample is placed over the specimen stage. A condensor lens containing an aperture diaphragm is located under the stage, will focus the light ray on the sample or specimen.
The light rays will pass through the specimen sample and then it will be collected by an objective lens located over the stage.
The objective lens will form a magnified image of the specimen and then transmit it yo the eyepiece, where the viewer will observe a dark image against the bright field.
During the transmission through the specimen, some of the light rays are absorbed by the stains, pigmentation, or dense areas of the specimen.
Advantages:
- It is easy to use
- Low Price
- These are compact in size and easy to carry.
- Both stained and unstained specimens can be observed
Disadvantages:
- Aperture diaphgram adds greater contrast which cn create distortion.
- Living Specimen of Bacteris can not be observed under a bright field microscope.
- Most of the specimens required to be stained to visualize under this microscope, because of its low contrast.
- Specimens can be damaged by the uses of coverslips
- The bright field microscope required a strong source of light to illuminate the specimen.
Application of Bright Field Microscopy:
- Used in blood counting
- Used to examine the bacterial cells.
- Used to examine fungal cells
- It also used in forensic laboratories
- Used to study Plant Cells
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