Wednesday, March 11, 2009

A Dissecting Microscope For School Use

Anyone who has taken high school biology has encountered a dissecting microscope; it was usually accompanied by a frog. The trauma involved in having to chloroform destroy a frog in the name of education may, however, have rendered you oblivious to the workings of the dissecting microscope, so here is a refresher course on how it was constructed and how it worked.
Construction Of A Dissecting Microscope
The dissecting microscope, like all microscopes, has a tube with a lens at its upper opening, through which you look to view the specimen lying beneath the tube’s lower end. The upper end of the tube will also have some form of nose piece to help your head remain steady while you do your viewing.
The lower end of the dissecting microscope contains the second lens, known as the “objective“ lens. The type of objective lens being used will depend on how fine a focus you need to examine your specimen. Your dissecting microscope will have two more light-condensing lenses in its condenser; these lenses are responsible for the microscope’s magnification capacity.
The dissecting microscope’s condenser is centered above the middle of the microscope’s stage, on which the slide bearing the specimen ifs placed for examination. The best dissecting microscopes have adjustable stages which can be manipulated without the microscope’s user having to remove his or her eyes from the eyepiece.
The dissecting microscope’s stage is positioned above its diaphragm, the function of which is to control the amount of light being transmitted through the slide and specimen. The light itself is also below the dissecting microscope’s stage, and is either a halogen or fluorescent bulb. It is the manipulation of the light’s reflection on the specimen that causes the dissecting microscope to magnify what the user sees.
Caring For A Dissecting Microscope
Dissecting microscopes, like all others, require special care; their lenses should be kept dust and smudge free with dry, soft cloths and they should be stored, when not in use, in dust covers. They should also be stored away from dampness.
Those handling a dissecting microscope should always carry it in both hands. That is the best way to avoid either dropping it or bumping it against other objects; either of which will ruin the alignment of the lenses. The dissecting microscope is most secure when its user holds the microscope arm in one hand and supports its base in the other.
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Saturday, March 7, 2009

Microscope FAQs


A microscope is an optical instrument used to view extremely small objects, which are difficult to be seen by the naked eye.
What are the different parts of a microscope?
The major parts of a microscope are the lenses, the tube, the arm, the illuminator, and the stage. Two kinds of lenses are used ? eyepiece lens (ocular) and the objective lens. Both the lenses are connected using the tube. The place where the viewing object is placed is called the stage. The arm connects the stage and the lens. A microscope has two adjustment knobs, which help to focus the lenses.
How does a microscope work?
The object or the specimen is kept close to the objective lens, so that the light from it focuses around 160 mm inside the microscope. This creates an enlarged and inverted image of the object. The image is then directed straight into the eye with the help of the ocular or the eyepiece.
How to use a microscope?
Place the specimen on the microscope stage and fix it with stage clips. Turn the coarse focus knob to bring the objective lens close to the specimen. Then, adjust the illuminator and diaphragm by looking through the eyepiece. Slowly turn the adjustment knob, until the image is focused.
What are the different types of microscopes?
Basically, there are three types of microscopes: electron, confocal, and compound. Electron microscopes are sophisticated magnifying devices using a high energetic beam of electrons. They can be further classified as scanning electron microscope (SEM) and transmission electron microscope (TEM). The confocal microscopes use a laser beam to illuminate the objects. Compound microscopes are the simplest type of microscopes. In this, the object or the specimen is illuminated using bulb light or light from the sun. Depending on specific applications, you can choose from portable student microscopes, surgical microscopes, metallurgical microscopes, measuring microscopes and industrial microscopes.
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Friday, March 6, 2009

The History of the Microscope

The first microscope was created hundreds of years ago. In the passing centuries, microscopes evolved into powerful, precise tools that allow scientists to view tiny objects at a level of detail that seems unreal. There are a wide array of available microscopes, from the compound microscopes commonly found in high school science classrooms to powerful scanning tunneling and electron microscopes used by Nobel Prize winners.
Most historians agree that two Dutchman made the first microscope in 1590. Zaccharias Janssen and his son Hans were two eyeglass makers who experimented with putting multiple lenses together in a tube. They found that objects under the tube were greatly enlarged. Over the next hundred years, scientists Robert Hooke, Anton van Leeuwenhoek, and others further refined the work of the Janssens and used microscopes to examine insects, blood, and other items. Scientists have continued microscopes into the present day. Now, microscopes can show tiny particles that are unseen by the naked eye in extremely exact detail.
Microscopes operate on several principles. Most common microscopes have two different lenses. Viewers look through the ocular lens, also known as the eyepiece. There is another lens, called the objective lens at the end of the ocular lens. The objective lens is a sphere shaped lens located above the stage of the microscope. People place the object they want to examine on the stage and can adjust the lenses to bring the object into focus. Most microscopes have an adjustment knob for coarse focus and one for fine focus. Many microscopes have several objective lenses with different strengths for users to choose from. The lenses are arranged on a circular platform that can be rotated to have the different lenses put into place under the ocular lens. Microscopes also need a light source of some kind underneath the stage. Most commercial microscopes have a light bulb, but many high-end microscopes use lasers or electrons for illumination.
Microscopes have been used to make countless vital scientific discoveries. They are invaluable tools used in a variety of scientific fields that enable researchers to make discoveries that would be impossible with the naked eye.
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