The development history of microscope

The microscope is one of the greatest inventions of the 20th century. Before it was invented, human's concept of the world around him was limited to what the naked eye could see, or through holding a lens.

Microscope shows a brand-new world in human vision. For the first time, people saw hundreds of "new" tiny animals and plants, and all the internal structures from human body to plant fibers. Microscopes also help scientists discover new species and help doctors treat diseases.

The earliest microscope was made in Holland at the end of16th century. The inventor is the Dutch optician Yas Zhan Sen, or another Dutch scientist Hans Lipper. They made a simple microscope with two lenses, but they didn't make any important observations with these instruments.

Later, two people began to use microscopes in science. The first is the Italian scientist Galileo. He described the compound eyes of insects for the first time after observing them through a microscope. The second is the Dutch linen dealer Levin Hooke (1632-1723), who taught himself to grind lenses. For the first time, he described many tiny plants and animals invisible to the naked eye.

193 1 year, Ernst ruska invented an electron microscope, which completely changed biology. This enables scientists to observe objects as small as a millionth of a millimeter. 1986 won the Nobel Prize.

Extended data:

The principle of imaging:

1, optical microscope

Optical microscope is mainly composed of eyepiece, objective lens, objective table and reflector. Both eyepiece and objective lens are convex lenses with different focal lengths. The focal length of the convex lens of the objective lens is smaller than that of the convex lens of the eyepiece. The objective lens is equivalent to the lens of the projector, and the object is inverted and enlarged through the objective lens. The eyepiece is equivalent to an ordinary magnifying glass, and the real image becomes an upright and enlarged virtual image through the eyepiece.

All the objects seen by the microscope are inverted and magnified virtual images. Mirrors are used to reflect and illuminate the observed objects. Mirrors generally have two reflective surfaces: one is a flat mirror, which is used when the light is strong; One is concave mirror, which is used when the light is weak, and it can concentrate the light.

2. Electron microscope

Electron microscope is an instrument that uses electron beam and electron lens instead of light beam and optical lens according to the principle of electron optics, so that the fine structure of matter can be imaged at a very high magnification.

The resolving power of an electron microscope is expressed by the minimum distance between two adjacent points that it can resolve. In 1970s, the resolution of transmission electron microscope was about 0.3 nm (human eye resolution was about 0. 1 mm).

At present, the maximum magnification of electron microscope is more than 3 million times, while the maximum magnification of optical microscope is about 2000 times, so some heavy metal atoms and ordered atomic lattices in crystals can be directly observed through electron microscope.

Maintenance of microscope

1. When the microscope is taken out of the wooden box or box, hold the mirror arm tightly with the right hand and the mirror base firmly with the left hand, and take it out gently. Do not extract with one hand to prevent the microscope from falling, and then gently put it on the practice table or in a wooden box.

2. When the microscope is placed on the practice table, put one end of the lens holder first, and then stabilize all the lens holders. Never let the lens holder contact the table at the same time, so the vibration is too great and the lens and fine-tuning device are easy to be damaged.

3. The microscope should always be kept clean to avoid oil and dust adhesion. If the lens part is not clean, gently wipe it with a mirror cleaning paper. If there is oil stain, first wipe the mirror cleaning paper with a little xylene.

4. The microscope can't be used in the sun.

5. Don't take out the eyepiece and objective lens casually. When the eyepiece must be taken out, cover the upper opening of the lens barrel with a clean cloth to prevent dust from falling into the lens barrel. When replacing the objective lens, take it off and put it upside down under a clean table, and then put it into the tube where the objective lens is placed in a wooden box.

6. After the microscope is used up, take out the specimen, lower it through the condenser, then turn the objective lens into a figure of eight, and turn the coarse adjuster to lower the lens barrel to avoid collision between the objective lens and the condenser.

7. The microscope should be placed in a dry place to prevent mildew.

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