Microscope definition for 3. What is a microscope? Subtypes of light microscopes

A microscope is a device designed to magnify the image of objects of study to view details of their structure hidden to the naked eye. The device provides magnification of tens or thousands of times, which allows for research that cannot be obtained using any other equipment or device.

Microscopes are widely used in medicine and laboratory research. With their help, dangerous microorganisms and viruses are initialized in order to determine the treatment method. The microscope is indispensable and is constantly being improved. For the first time, a semblance of a microscope was created in 1538 by the Italian physician Girolamo Fracastoro, who decided to install two optical lenses, similar topics that are used in glasses, binoculars, telescopes and magnifying glasses. Galileo Galilei, as well as dozens of world famous scientists, worked on improving the microscope.

Device

There are many types of microscopes that differ in design. Most models share a similar design, but with minor technical features.

In the vast majority of cases, microscopes consist of a stand on which 4 main elements are fixed:

• Lens.
• Eyepiece.
• Lighting system.
• Subject table.

Lens

The lens is a complex optical system that consists of glass lenses running one after another. The lenses are made in the form of tubes, inside of which up to 14 lenses can be fixed. Each of them magnifies the image, removing it from the surface of the lens in front. Thus, if one magnifies an object by 2 times, the next one will magnify this projection even more, and so on until the object is displayed on the surface of the last lens.

Each lens has its own focusing distance. In this regard, they are tightly fixed in the tube. If any of them are moved closer or further, you will not be able to get a clear magnification of the image. Depending on the characteristics of the lens, the length of the tube in which the lens is enclosed may vary. In fact, the higher it is, the more enlarged the image will be.

Eyepiece

The microscope eyepiece also consists of lenses. It is designed so that the operator who works with the microscope can put his eye on it and see a magnified image on the lens. The eyepiece has two lenses. The first is located closer to the eye and is called the ocular, and the second field. With the help of the latter, the image magnified by the lens is adjusted for its correct projection onto the retina of the human eye. This is necessary in order to remove visual perception defects by adjustment, since each person focuses at a different distance. The field lens allows you to adjust the microscope to this feature.

Lighting system

To view the object being studied, it is necessary to illuminate it, since the lens blocks natural light. As a result, looking through the eyepiece you can always see only a black or gray image. A lighting system was developed specifically for this purpose. It can be made in the form of a lamp, LED or other light source. At the most simple models light rays are received from an external source. They are directed to study the subject using mirrors.

Subject table

The last important and easiest to manufacture part of a microscope is the stage. The lens is directed at it, since it is on it that the object to be studied is fixed. The table has a flat surface, which allows you to fix the object without fear that it will move. Even the slightest movement of the research object under magnification will be enormous, so finding the original point that was examined again will not be easy.

Types of microscopes

Over the vast history of the existence of this device, several microscopes have been developed that differ significantly in operating principles.

Among the most frequently used and in demand types of this equipment are the following types:

• Optical.
• Electronic.
• Scanning probes.
• X-ray.

Optical

An optical microscope is the most inexpensive and simple device. This equipment allows you to magnify the image 2000 times. It's pretty big indicator, which allows you to study the structure of cells, the surface of tissue, find defects in artificially created objects, etc. It is worth noting that to achieve such high magnification the device must be of very high quality, so it is expensive. The vast majority of optical microscopes are made much simpler and have relatively low magnification. Educational types of microscopes are represented by optical ones. This is due to their lower cost, as well as the not too high magnification factor.

Typically, an optical microscope has several lenses that are mounted on a movable stand. Each of them has its own degree of magnification. While examining an object, you can move the lens to the working position and study it at a certain magnification. If you want to bring the image even closer, you just need to switch to an even more magnifying lens. These devices do not have ultra-precise adjustment. For example, if you only need to zoom in on the image a little, then by switching to another lens, you can zoom it in tens of times, which will be excessive and will not allow you to correctly perceive the enlarged image and avoid unnecessary details.

Electron microscope

Electronic is a more advanced design. It provides image magnification of at least 20,000 times. The maximum magnification of such a device is possible by 10 6 times. The peculiarity of this equipment is that instead of a beam of light like optical ones, they send a beam of electrons. The image is obtained through the use of special magnetic lenses that respond to the movement of electrons in the instrument column. The beam direction is adjusted using . These devices appeared in 1931. In the early 2000s, computer equipment and electron microscopes began to be combined, which significantly increased the magnification factor, the adjustment range, and made it possible to capture the resulting image.

Electronic devices, for all their advantages, are more expensive and require special operating conditions. To obtain a high-quality, clear image, it is necessary that the subject of study be in a vacuum. This is because air molecules scatter electrons, affecting image clarity and preventing precise adjustments. In this regard, this equipment is used in laboratory conditions. Another important requirement for using electron microscopes is the absence of external magnetic fields. Because of this, the laboratories in which they are used have very thick insulated walls or are located in underground bunkers.

Such equipment is used in medicine, biology, as well as in various industries.

Scanning probe microscopes

Scanning probe microscope allows you to obtain an image from an object by examining it using a special probe. The result is a three-dimensional image with accurate data on the characteristics of objects. This equipment has high resolution. This is a relatively new equipment that was created several decades ago. Instead of a lens, these devices have a probe and a system for moving it. The image obtained from it is registered by a complex system and recorded, after which a topographical picture of the enlarged objects is created. The probe is equipped with sensitive sensors that respond to the movement of electrons. There are also probes that operate optically by magnifying them due to the installation of lenses.

Probes are often used to obtain data on the surface of objects with complex terrain. They are often lowered into pipes, holes, and small tunnels. The only condition is that the diameter of the probe matches the diameter of the object being studied.

This method is characterized by a significant measurement error, since the resulting 3D picture is difficult to decipher. There are many details that are distorted by the computer during processing. The initial data is processed mathematically using specialized software.

X-ray microscopes

X-ray microscope belongs to laboratory equipment, used to study objects whose dimensions are comparable to the x-ray wavelength. Increase efficiency of this device located between optical and electronic devices. They are sent to the object being studied x-rays, after which sensitive sensors react to their refraction. As a result, a picture of the surface of the object being studied is created. Due to the fact that X-rays can pass through the surface of an object, such equipment allows not only to obtain data about the structure of the object, but also its chemical composition.

X-ray equipment is commonly used to evaluate the quality of thin coatings. It is used in biology and botany, as well as for the analysis of powder mixtures and metals.

The human eye is designed in such a way that it cannot see an object whose dimensions do not exceed 0.1 mm. In nature, there are objects whose sizes are much smaller. These are microorganisms, cells of living tissues, structural elements of substances and much more.

Even in ancient times, polished natural crystals were used to improve vision. With the development of glassmaking, glass lentils - lenses - began to be produced. R. Bacon in the 13th century. advised people with poor vision place convex glass on objects in order to see them better. At the same time, glasses consisting of two connected lenses appeared in Italy.

In the 16th century craftsmen in Italy and the Netherlands who made spectacle glasses knew about the property of a system of two lenses to produce an enlarged image. One of the first such devices was made in 1590 by the Dutchman Z. Jansen.

Despite the fact that the magnifying ability of spherical surfaces and lenses was known back in the 13th century, until the beginning of the 17th century. none of the natural scientists even tried to use them to observe the smallest objects inaccessible to the naked human eye.

The word “microscope”, derived from two Greek words – “small” and “look”, was introduced into scientific use by a member of the Academy “Dei Lyncei” (lynx-eyed) Desmikian at the beginning of the 17th century.

In 1609, Galileo Galilei, while studying the telescope he designed, used it as a microscope. To do this, he changed the distance between the lens and the eyepiece. Galileo was the first to come to the conclusion that the quality of lenses for glasses and telescopes should be different. He created a microscope by selecting a distance between lenses that would magnify not distant objects, but nearby objects. In 1614, Galileo examined insects using a microscope.

Galileo's student E. Torricelli adopted the art of grinding lenses from his teacher. In addition to making spotting scopes, Torricelli constructed simple microscopes, consisting of one tiny lens, which he obtained from one drop of glass by melting a glass rod over a fire.

In the 17th century The simplest microscopes were popular, consisting of a magnifying glass - a biconvex lens mounted on a stand. An object table on which the object in question was placed was also mounted on the stand. Below the table there was a mirror of a flat or convex shape, which reflected the sun's rays onto the object and illuminated it from below. To improve the image, the magnifying glass was moved relative to the stage using a screw.

In 1665, the Englishman R. Hooke, using a microscope using small glass beads, discovered the cellular structure of animal and plant tissues.

Hooke's contemporary, the Dutchman A. van Leeuwenhoek, manufactured microscopes consisting of small biconvex lenses. They provided 150–300x magnification. Using his microscopes, Leeuwenhoek studied the structure of living organisms. In particular, he discovered the movement of blood in blood vessels and red blood cells, sperm, described the structure of muscles, skin scales and much more.

Leeuwenhoek discovered new world– the world of microorganisms. He described many species of ciliates and bacteria.

The Dutch biologist J. Swammerdam made many discoveries in the field of microscopic anatomy. He studied the anatomy of insects in most detail. In the 30s XVIII century he produced a lavishly illustrated work called Nature's Bible.

Methods for calculating the optical components of a microscope were developed by the Swiss L. Euler, who worked in Russia.

The most common microscope design is as follows: the object being examined is placed on a stage. Above it is a device in which the objective lenses and tube - a tube with an eyepiece - are mounted. The observed object is illuminated using a lamp or sunlight, inclined mirror and lens. Diaphragms installed between the light source and the object limit the luminous flux and reduce its share diffused light. A mirror is installed between the diaphragms, changing the direction of the light flux by 90°. A condenser concentrates a beam of light onto an object. The lens collects the rays scattered by the object and forms a magnified image of the object, viewed using an eyepiece. The eyepiece works like a magnifying glass, providing additional magnification. The microscope magnification ranges from 44 to 1500 times.

In 1827, J. Amici used an immersion lens in a microscope. In it, the space between the object and the lens is filled with immersion liquid. Such liquids are used various oils(cedar or mineral), water or an aqueous solution of glycerin, etc. Such lenses allow you to increase the resolution of the microscope and improve image contrast.

In 1850, the English optician G. Sorby created the first microscope for observing objects in polarized light. Such devices are used to study crystals, metal samples, animal and plant tissues.

The beginning of interference microscopy was laid in 1893 by the Englishman J. Sirks. Its essence is that each beam entering the microscope splits into two. One of the resulting rays is directed towards the observed particle, the second - past it. At the eyepiece, both beams are reconnected and interference occurs between them. Interference microscopy allows the study of living tissues and cells.

In the 20th century appeared various types microscopes with different purposes, designs that allow the study of objects in wide ranges spectrum

Thus, in inverted microscopes the objective is located under the observed object, and the condenser is located on top. The direction of the rays is changed using a system of mirrors, and they enter the observer’s eye, as usual, from bottom to top. These microscopes are designed to study bulky objects that are difficult to position on the stage of conventional microscopes. They are used to study tissue cultures, chemical reactions, determine the melting points of materials. These microscopes are most widely used in metallography for observing the surfaces of metals, alloys and minerals. Inverted microscopes can be equipped with special devices for microphotography and microcinema.

Fluorescent microscopes are equipped with replaceable light filters that make it possible to isolate in the illuminator radiation that part of the spectrum that causes luminescence of the object under study. Special filters transmit only luminescent light from the object. The light sources in such microscopes are ultra-high-pressure mercury lamps that emit ultraviolet rays and rays in the short-wave range of the visible spectrum.

Ultraviolet and infrared microscopes are used to study areas of the spectrum that are inaccessible to the human eye. The optical circuits are similar to those of conventional microscopes. The lenses of these microscopes are made of materials that are transparent to ultraviolet (quartz, fluorite) and infrared (silicon, germanium) rays. They are equipped with cameras that record visible image and electron-optical converters that turn an invisible image into a visible one.

A stereo microscope provides a three-dimensional image of an object. These are actually two microscopes, made in a single design in such a way that the right and left eyes observe the object from different angles. They have found application in microsurgery and the assembly of miniature devices.

The comparison microscopes are two conventional microscopes combined with a single eyepiece system. Using such microscopes, you can observe two objects at once, comparing their visual characteristics.

In television microscopes, the image of the drug is converted into electrical signals that reproduce this image on the screen of a cathode ray tube. These microscopes allow you to change the brightness and contrast of the image. With their help, you can study objects at a safe distance that are dangerous to view at close range, such as radioactive substances.

The best optical microscopes allow you to magnify observed objects by approximately 2000 times. Further magnification is not possible because the light bends around the illuminated object, and if its dimensions are smaller than the wavelength, such an object becomes invisible. The minimum size of an object that can be seen in an optical microscope is 0.2–0.3 micrometers.

In 1834, W. Hamilton established that there is an analogy between the passage of light rays in optically inhomogeneous media and the trajectories of particles in force fields. The possibility of creating an electron microscope appeared in 1924 after L. De Broglie put forward the hypothesis that all types of matter without exception - electrons, protons, atoms, etc. - are characterized by particle-wave dualism, that is, they have the properties of both particles and and waves. The technical prerequisites for the creation of such a microscope appeared thanks to the research of the German physicist H. Busch. He investigated the focusing properties of axisymmetric fields and in 1928 developed a magnetic electron lens.

In 1928, M. Knoll and M. Ruska began creating the first magnetic transmission microscope. Three years later, they obtained an image of an object formed using beams of electrons. In 1938, M. von Ardenne in Germany and in 1942, V. K. Zworykin in the USA built the first scanning electron microscopes operating on the scanning principle. In them, a thin electron beam (probe) sequentially moved across the object from point to point.

In an electron microscope, unlike an optical microscope, electrons are used instead of light rays, and electromagnetic coils or electron lenses are used instead of glass lenses. The source of electrons for illuminating an object is an electron “gun”. In it, the source of electrons is a metal cathode. The electrons are then collected into a beam using a focusing electrode and, under the influence of a strong electric field acting between the cathode and anode, gain energy. To create a field, voltages of up to 100 kilovolts or more are applied to the electrodes. The voltage is regulated in steps and is highly stable - in 1–3 minutes it changes by no more than 1–2 ppm from the original value.

Coming out of the electron "gun", a beam of electrons is directed to an object using a condenser lens, scattered on it and focused by an object lens, which creates an intermediate image of the object. The projection lens recollects the electrons and creates a second, even larger image on the fluorescent screen. On it, under the influence of electrons striking it, a luminous picture of the object appears. If you place a photographic plate under the screen, you can photograph this image.

Excellent definition

Incomplete definition ↓

All dictionaries Automobile dictionary Architectural dictionary Astronomical dictionary Biblical encyclopedia Business dictionary Biographical dictionary Large accounting dictionary Jeans dictionary Culinary dictionary Medical dictionary Marine dictionary Printing dictionary Political dictionary Psychological Dictionary Religious dictionary Sexological dictionary Dictionary of thieves' jargon Dictionary of geographical names Dahl's dictionary Efremova's dictionary Dictionary of names Dictionary foreign words Dictionary of computer jargon Dictionary of resorts Dictionary medicinal plants Dictionary of logic Dictionary of measures Dictionary of fashion Dictionary of youth slang Dictionary of peoples Dictionary of numismatist Ozhegov's Dictionary Dictionary of art Dictionary of landscape design Dictionary of mythology Dictionary of Russian surnames Dictionary of symbols Dictionary of synonyms Dictionary of phraseological units Dictionary of epithets Construction dictionary Dictionary Ushakova Financial Dictionary Encyclopedic Dictionary Collier's Encyclopedia Vasmer's Etymological Dictionary Ethnographic Dictionary

What is a microscope? Meaning and interpretation of the word mikroskop, definition of the term

microscope -

an optical instrument with one or more lenses for producing magnified images of objects not visible to the naked eye. Microscopes can be simple or complex. A simple microscope is a single lens system. A simple microscope can be considered an ordinary magnifying glass - a plano-convex lens. A compound microscope (often called simply a microscope) is a combination of two simple ones.

A compound microscope provides greater magnification than a simple one and has greater resolution. Resolution is the ability to distinguish details of a sample. An enlarged image with no details visible provides little useful information.

A complex microscope has a two-stage design. One system of lenses, called an objective, is brought close to the sample; it creates a magnified and resolved image of the object. The image is further magnified by another lens system called an eyepiece, which is placed closer to the viewer's eye. These two lens systems are located at opposite ends of the tube.

Working with a microscope. The illustration shows a typical biological microscope. The tripod stand is made in the form of a heavy casting, usually horseshoe-shaped. A tube holder is attached to it on a hinge, carrying all the other parts of the microscope. The tube in which the lens systems are mounted allows them to be moved relative to the sample for focusing. The lens is located at the lower end of the tube. Typically, a microscope is equipped with several objectives of different magnifications on a turret, which allows them to be installed in a working position on the optical axis. The operator, examining a sample, begins, as a rule, with a lens that has lowest magnification and the widest field of view, finds the details that interest him, and then examines them using a high-magnification lens. The eyepiece is mounted at the end of a retractable holder (which allows you to change the length of the tube when necessary). The entire tube with objective and eyepiece can be moved up and down to focus the microscope.

The sample is usually taken as a very thin transparent layer or section; it is placed on a rectangular glass plate, called a slide, and covered on top with a thinner, smaller glass plate, called a coverslip. The sample is often stained chemicals to increase contrast. The glass slide is placed on the stage so that the sample is located above the central hole of the stage. The stage is usually equipped with a mechanism to move the sample smoothly and accurately within the field of view.

Under the object stage there is a holder for the third lens system - a condenser, which concentrates the light on the sample. There can be several condensers, and an iris diaphragm is located here to adjust the aperture.

Even lower is a lighting mirror installed in a universal joint, which reflects the light of the lamp onto the sample, due to which the entire optical system of the microscope creates a visible image. The eyepiece can be replaced with a photo attachment, and then the image will be formed on photographic film. Many research microscopes are equipped with a special illuminator, so that an illumination mirror is not necessary.

Increase. The magnification of a microscope is equal to the product of the objective magnification and the eyepiece magnification. For a typical research microscope The magnification of the eyepiece is 10, and the magnification of the objectives is 10, 45 and 100. Therefore, the magnification of such a microscope is from 100 to 1000. The magnification of some microscopes reaches 2000. Increasing the magnification even more does not make sense, since the resolution does not improve; on the contrary, the image quality deteriorates.

Theory. A consistent theory of the microscope was given by the German physicist Ernst Abbe at the end of the 19th century. Abbe found that resolution (the minimum possible distance between two points that are separately visible) is given by

where R is the resolution in micrometers (10-6 m), . - wavelength of light (created by the illuminator), μm, n - refractive index of the medium between the sample and the lens, a. - half the input angle of the lens (the angle between the outer rays of the conical light beam entering the lens). Abbe called the quantity numerical aperture (it is denoted by the symbol NA). From the above formula it is clear that the greater the NA and the shorter the wavelength, the smaller the resolved details of the object under study.

The numerical aperture not only determines the resolution of the system, but also characterizes the lens aperture: the light intensity per unit image area is approximately equal to the square of NA. For a good lens, the NA value is approximately 0.95. The microscope is usually designed so that its total magnification is approx. 1000 NA.

Lenses. There are three main types of lenses, differing in the degree of correction of optical distortions - chromatic and spherical aberrations. Chromatic aberration occurs when light waves of different wavelengths are focused at different points on the optical axis. As a result, the image appears colored. Spherical aberrations are caused by the fact that light passing through the center of the lens and light passing through its peripheral part are focused at different points on the axis. As a result, the image appears unclear.

Achromatic lenses are currently the most common. In them, chromatic aberrations are suppressed through the use of glass elements with different dispersion, ensuring the convergence of the extreme rays of the visible spectrum - blue and red - into one focus. A slight coloration of the image remains and sometimes appears as faint green stripes around the object. Spherical aberration can only be corrected for one color.

Fluorite lenses use glass additives to improve color correction to the point that coloration is almost completely eliminated from the image.

Apochromatic lenses are the lenses with the most complex color correction. They not only almost completely eliminate chromatic aberrations, but also correct spherical aberrations for not one, but two colors. Increasing apochromats for blue somewhat more than for red, and therefore they require special “compensating” eyepieces.

Most lenses are "dry", i.e. they are designed to work in conditions where the gap between the lens and the sample is filled with air; the NA value for such lenses does not exceed 0.95. If a liquid (oil or, more rarely, water) is introduced between the objective and the sample, an “immersion” objective is obtained with an NA value as high as 1.4 and a corresponding improvement in resolution.

Currently, the industry produces and various kinds special lenses. These include flat-field lenses for microphotography, stress-free (relaxed) lenses for working in polarized light, and lenses for examining opaque metallurgical samples illuminated from above.

Condensers. The condenser forms a cone of light directed at the sample. Typically, a microscope is equipped with an iris diaphragm to match the aperture of the light cone with the aperture of the objective, thereby providing maximum resolution and maximum image contrast. (Contrast in microscopy has the same important, as in television technology.) The simplest condenser, quite suitable for most general-purpose microscopes, is the two-lens Abbe condenser. Larger aperture lenses, especially oil immersion lenses, require more complex corrected condensers. Maximum aperture oil objectives require a special condenser that has oil immersion contact with the bottom surface of the slide on which the sample rests.

Specialized microscopes. Due to different requirements Science and technology have developed many special types of microscopes.

A stereoscopic binocular microscope, designed to obtain a three-dimensional image of an object, consists of two separate microscopic systems. The device is designed for small magnification (up to 100). Typically used for assembly of miniature electronic components, technical inspection, surgical operations.

A polarizing microscope is designed to study the interaction of samples with polarized light. Polarized light often makes it possible to reveal the structure of objects that lies beyond the limits of conventional optical resolution.

A reflective microscope is equipped with mirrors instead of lenses that form an image. Since it is difficult to make a mirror lens, there are very few fully reflective microscopes, and mirrors are currently used mainly only in attachments, for example, for microsurgery of individual cells.

Fluorescent microscope - illuminating the sample with ultraviolet or blue light. The sample, absorbing this radiation, emits visible luminescence light. Microscopes of this type are used in biology, as well as in medicine - for diagnostics (especially cancer).

The dark-field microscope circumvents the difficulties associated with the fact that living materials are transparent. The sample is viewed under such “oblique” lighting that direct light cannot enter the lens. The image is formed by light diffracted by an object, causing the object to appear very light against a dark background (with very high contrast).

A phase contrast microscope is used to examine transparent objects, especially living cells. Thanks to special devices, part of the light passing through the microscope turns out to be phase-shifted by half the wavelength relative to the other part, which determines the contrast in the image.

An interference microscope is further development phase contrast microscope. It involves interference between two light beams, one of which passes through the sample and the other is reflected. This method produces colored images that provide very valuable information when studying living material. See also ELECTRON MICROSCOPE; OPTICAL INSTRUMENTS; OPTICS.

Microscope

an optical instrument with one or more lenses for producing magnified images of objects not visible to the naked eye. Microscopes can be simple or complex. A simple microscope is a single lens system. A simple microscope can be considered an ordinary magnifying glass - a plano-convex lens. A compound microscope (often called simply a microscope) is a combination of two simple ones. A compound microscope provides greater magnification than a simple one and has greater resolution. Resolution is the ability to distinguish details of a sample. An enlarged image with no details visible provides little useful information. A complex microscope has a two-stage design. One system of lenses, called an objective, is brought close to the sample; it creates a magnified and resolved image of the object. The image is further magnified by another lens system called an eyepiece, which is placed closer to the viewer's eye. These two lens systems are located at opposite ends of the tube. Working with a microscope. The illustration shows a typical biological microscope. The tripod stand is made in the form of a heavy casting, usually horseshoe-shaped. A tube holder is attached to it on a hinge, carrying all the other parts of the microscope. The tube in which the lens systems are mounted allows them to be moved relative to the sample for focusing. The lens is located at the lower end of the tube. Typically, a microscope is equipped with several objectives of different magnifications on a turret, which allows them to be installed in a working position on the optical axis. The operator, examining a sample, usually starts with the lens that has the lowest magnification and the widest field of view, finds the details that interest him, and then examines them using a lens with higher magnification. The eyepiece is mounted at the end of a retractable holder (which allows you to change the length of the tube when necessary). The entire tube with objective and eyepiece can be moved up and down to focus the microscope. The sample is usually taken as a very thin transparent layer or section; it is placed on a rectangular glass plate, called a slide, and covered on top with a thinner, smaller glass plate, called a coverslip. The sample is often stained with chemicals to increase contrast. The glass slide is placed on the stage so that the sample is located above the central hole of the stage. The stage is usually equipped with a mechanism to move the sample smoothly and accurately within the field of view. Under the object stage there is a holder for the third lens system - a condenser, which concentrates the light on the sample. There can be several condensers, and an iris diaphragm is located here to adjust the aperture. Even lower is a lighting mirror installed in a universal joint, which reflects the light of the lamp onto the sample, due to which the entire optical system of the microscope creates a visible image. The eyepiece can be replaced with a photo attachment, and then the image will be formed on photographic film. Many research microscopes are equipped with a special illuminator, so that an illumination mirror is not necessary. Increase. The magnification of a microscope is equal to the product of the objective magnification and the eyepiece magnification. For a typical research microscope, the magnification of the eyepiece is 10, and the magnification of the objectives is 10, 45 and 100. Therefore, the magnification of such a microscope ranges from 100 to 1000. The magnification of some microscopes reaches 2000. Increasing the magnification even more does not make sense, since the resolution at the same time not improving; on the contrary, the image quality deteriorates. Theory. A consistent theory of the microscope was given by the German physicist Ernst Abbe at the end of the 19th century. Abbe found that resolution (the minimum possible distance between two points that are separately visible) is given by where R is the resolution in micrometers (10-6 m), . - wavelength of light (created by the illuminator), μm, n - refractive index of the medium between the sample and the lens, a. - half the input angle of the lens (the angle between the outer rays of the conical light beam entering the lens). Abbe called the quantity numerical aperture (it is denoted by the symbol NA). From the above formula it is clear that the greater the NA and the shorter the wavelength, the smaller the resolved details of the object under study. The numerical aperture not only determines the resolution of the system, but also characterizes the lens aperture: the light intensity per unit image area is approximately equal to the square of NA. For a good lens, the NA value is approximately 0.95. The microscope is usually designed so that its total magnification is approx. 1000 NA. Lenses. There are three main types of lenses, differing in the degree of correction of optical distortions - chromatic and spherical aberrations. Chromatic aberration occurs when light waves of different wavelengths are focused at different points on the optical axis. As a result, the image appears colored. Spherical aberrations are caused by the fact that light passing through the center of the lens and light passing through its peripheral part are focused at different points on the axis. As a result, the image appears unclear. Achromatic lenses are currently the most common. In them, chromatic aberrations are suppressed through the use of glass elements with different dispersion, ensuring the convergence of the extreme rays of the visible spectrum - blue and red - into one focus. A slight coloration of the image remains and sometimes appears as faint green stripes around the object. Spherical aberration can only be corrected for one color. Fluorite lenses use glass additives to improve color correction to the point that coloration is almost completely eliminated from the image. Apochromatic lenses are the lenses with the most complex color correction. They not only almost completely eliminate chromatic aberrations, but also correct spherical aberrations for not one, but two colors. The magnification of apochromats for blue is slightly greater than for red, and therefore they require special “compensating” eyepieces. Most lenses are "dry", i.e. they are designed to work in conditions where the gap between the lens and the sample is filled with air; the NA value for such lenses does not exceed 0.95. If a liquid (oil or, more rarely, water) is introduced between the objective and the sample, an “immersion” objective is obtained with an NA value as high as 1.4 and a corresponding improvement in resolution. Currently, the industry produces various types of special lenses. These include flat-field lenses for microphotography, stress-free (relaxed) lenses for working in polarized light, and lenses for examining opaque metallurgical samples illuminated from above. Condensers. The condenser forms a cone of light directed at the sample. Typically, a microscope is equipped with an iris diaphragm to match the aperture of the light cone with the aperture of the objective, thereby providing maximum resolution and maximum image contrast. (Contrast is as important in microscopy as it is in television technology.) The simplest condenser, quite suitable for most general-purpose microscopes, is the two-lens Abbe condenser. Larger aperture lenses, especially oil immersion lenses, require more complex corrected condensers. Maximum aperture oil objectives require a special condenser that has oil immersion contact with the bottom surface of the slide on which the sample rests. Specialized microscopes. Due to the various requirements of science and technology, many special types of microscopes have been developed. A stereoscopic binocular microscope, designed to obtain a three-dimensional image of an object, consists of two separate microscopic systems. The device is designed for small magnification (up to 100). Typically used for assembly of miniature electronic components, technical inspection, surgical operations. A polarizing microscope is designed to study the interaction of samples with polarized light. Polarized light often makes it possible to reveal the structure of objects that lies beyond the limits of conventional optical resolution. A reflective microscope is equipped with mirrors instead of lenses that form an image. Since it is difficult to make a mirror lens, there are very few fully reflective microscopes, and mirrors are currently used mainly only in attachments, for example, for microsurgery of individual cells. Fluorescent microscope - illuminating the sample with ultraviolet or blue light. The sample, absorbing this radiation, emits visible luminescence light. Microscopes of this type are used in biology, as well as in medicine - for diagnostics (especially cancer). The dark-field microscope circumvents the difficulties associated with the fact that living materials are transparent. The sample is viewed under such “oblique” lighting that direct light cannot enter the lens. The image is formed by light diffracted by an object, causing the object to appear very light against a dark background (with very high contrast). A phase contrast microscope is used to examine transparent objects, especially living cells. Thanks to special devices, part of the light passing through the microscope turns out to be phase-shifted by half the wavelength relative to the other part, which determines the contrast in the image. An interference microscope is a further development of the phase contrast microscope. It involves interference between two light beams, one of which passes through the sample and the other is reflected. This method produces colored images that provide very valuable information when studying living material. See also ELECTRON MICROSCOPE; OPTICAL INSTRUMENTS; OPTICS.

Tudupov Ayur

In his work, the student examines the history of the creation of the microscope. He also describes the experience of creating a simple microscope at home.

Download:

Preview:

Municipal educational institution "Mogoituy secondary school No. 1"

Research work on the topic

"What is a microscope"

Section: physics, technology

Completed by: 2nd grade student Tudupov Ayur

Head: Baranova I.V.

village Mogoituy

2013

Performance

Pulls out

2nd grade student of Municipal Educational Establishment Secondary School No. 1, Mogoituy Tudupov Ayur

Title of the research paper

“What is a microscope?”

Head of work

Baranova Irina Vladimirovna

Brief description (subject) of the work :

This work relates to experimental research and is an experimental - theoretical study.

Direction:

Physics, applied research(technique).

Brief description of the research work

Name "What is a microscope?"

Completed by Tudupov Ayur

Under the leadershipBaranova Irina Vladimirovna

The research work is devoted to the study of:creating a microscope using a drop of water

Where did your interest in this problem or question come from?I always wanted to have a microscope to see the invisible world

Where did we look for information to answer our questions?(indicate sources)

1. Internet
2. Encyclopedias
3. Consultation with teacher

What hypothesis was put forward:You can create a microscope with your own hands from a drop of water.

In the study we usedthe following methods:

Experiments:

1. Experiment No. 1 “Creation of a microscope.”
2. Working with books.

Conclusions:

1. You can make a simple microscope at home using available materials.
2. I learned what a microscope is made of.
3. Creating your own thing is very interesting, especially since a microscope is an interesting thing.

We plan to use photographs to present the research results.

Participant form

Work plan

1. Questionnaire of the author of the work - page 1
2. Contents - page 2
3. Brief description of the project - page 3
4. Introduction - page 4
5. Main part - pages 5 – 10
6. Experiment to create a microscope. - pp. 11-14
7. Conclusion - page 15
8. Literature and sources - page 16

INTRODUCTION

From the very early age Every day, at home, in kindergarten and at school, coming from a walk and after using the toilet, after playing and before eating, I hear the same thing: “Don’t forget to wash your hands!” And so I thought: “Why wash them so often? They’re already clean, aren’t they?” I asked my mother: “Why do you need to wash your hands?” Mom replied: “The hands, like all surrounding objects, contain many microbes that, if they get into the mouth with food, can cause illness.” I looked carefully at my hands, but I didn’t see any germs. And my mother said that microbes are very small and cannot be seen without special magnifying devices. Then I armed myself with a magnifying glass and began to look at everything that surrounded me. But I still didn’t see any microbes. My mother explained to me that germs are so small that they can only be seen under a microscope. We have microscopes at school, but you can't take them home and look for germs. And then I decided to make my own microscope.

Purpose of my research: assemble your microscope.

Project objectives:

1. Learn the history of the creation of the microscope.
2. Find out what microscopes are made of and what they can be.
3. Try to create your own microscope and test it.

My hypothesis : you can create a microscope with your own hands at home from a drop of water and available materials.

Main part

History of the creation of the microscope.

Microscope (from Greek - small and I look) - an optical device for obtaining magnified images of objects invisible to the naked eye.

It's a fascinating activity to look at something through a microscope. No worse computer games, and maybe even better. But who invented this miracle - the microscope?

In the Dutch city of Middelburg there lived a spectacle master three hundred and fifty years ago. He patiently polished glass, made glasses and sold them to everyone who needed it. He had two children - two boys. They loved to climb into their father’s workshop and play with his tools and glass, although this was forbidden to them. And then one day, when their father was away somewhere, the guys made their way to his workbench as usual - is there anything new that they can have fun with? On the table lay glasses prepared for glasses, and in the corner lay a short copper tube: from it the master was going to cut rings - frames for glasses. The guys squeezed into the ends of the tube spectacle glass. The older boy put the pipe to his eye and looked at the page of the open book that lay right there on the table. To his surprise, the letters became huge. The younger one looked into the receiver and screamed, amazed: he saw a comma, but what a comma - it looked like a thick worm! The guys pointed the tube at the glass dust left after polishing the glass. And they saw not dust, but a bunch of glass grains. The tube turned out to be downright magical: it greatly magnified all objects. The boys told their father about their discovery. He didn’t even scold them: he was so surprised by the extraordinary properties of the pipe. He tried to make another tube with the same glasses, long and extendable. The new tube increased the magnification even better. This was the first microscope. His

accidentally invented in 1590 by the spectacle maker Zacharias Jansen, or rather, by his children.

Similar thoughts about creating a magnifying device occurred to more than one Jansen: new devices were also invented by the Dutchman Jan Liepershey (also a “spectacle” specialist and also from Middelburg), and Jacob Metius. The Dutchman Cornelius Drebbel appeared in England, who invented a microscope with two biconvex lenses. When rumors spread in 1609 that in Holland there was a certain device for viewing tiny objects, Galileo the very next day understood the general idea of ​​​​the design and made a microscope in his laboratory, and in 1612 he had already started making microscopes. At first, no one called the created device a microscope; it was called a consecration. The familiar words “telescope” and “microscope” were first spoken by the Greek Demistian in 1614.

In 1697, the Great Embassy, ​​which included our Tsar Peter the Great, left Moscow abroad. In Holland, he heard that “a certain Dutchman Leeuwenhoek,” living in the city of Delft, was making amazing devices at home. With their help, he discovered thousands of little animals, more wonderful than the most outlandish overseas animals. And these little animals “nest” in water, in the air and even in a person’s mouth. Knowing the king’s curiosity, it is not difficult to guess that Peter immediately went to visit. The devices that the king saw were so-called simple microscopes (it was a magnifying glass with high magnification). However, Leeuwenhoek managed to achieve a magnification of 300 times, and this exceeded the capabilities of the best compound microscopes of the 17th century, which had both a lens and an eyepiece.

For a long time, the secret of “flea glass,” as Leeuwenhoek’s device was disparagingly called by envious contemporaries, could not be revealed. How could

it turns out that in the 17th century a scientist created devices that were close in some characteristics to the devices of the early 20th century? After all, with the technology of that time it was impossible to make a microscope. Leeuwenhoek himself did not reveal his secret to anyone. The secret of the “flea glass” was revealed only 315 years later, at the Novosibirsk State Medical Institute at the Department of General Biology and Fundamentals of Genetics. The secret had to be very simple, because Leeuwenhoek short term managed to produce many copies of his single-lens microscopes. Maybe he didn’t polish his magnifying lenses at all? Yes, fire did it for him! If you take a glass thread and place it in the flame of a burner, a ball will appear at the end of the thread - it was this that served as Leeuwenhoek’s lens. The smaller the ball, the greater the magnification that was achieved...

Peter the Great spent about two hours in 1697 at Levenguk - and kept looking and looking. And already in 1716, during his second trip abroad, the emperor acquired the first microscopes for the Kunstkamera. This is how a wonderful device appeared in Russia.

A microscope can be called a device that reveals secrets. Microscopes looked different over the years, but every year they became more and more complex, and they began to have many details.

This is what Jansen's first microscope looked like:

The first large compound microscope was made by English physicist Robert Hooke in the 17th century.

This is what microscopes looked like in the 18th century. There were many travelers in the 18th century. And they needed to have a travel microscope that would fit in a bag or jacket pocket. In the first half of the 18th century. widespread received the so-called “hand-held” or “pocket” microscope, designed by the English optician J. Wilson. This is what they looked like:

What does a microscope consist of?

All microscopes consist of the following parts:

Microscope part	What is it for?
eyepiece	magnifies the image received from the lens
lens	Ensures magnification of small objects
tube	telescope, connects the lens and eyepiece
adjustment screw	raises and lowers the tube, allows you to zoom in and out of the object of study
stage	the subject of consideration is placed on it
mirror	helps direct light through a hole on the stage.

There is also a backlight and clips.

I also learned what microscopes can be. In the modern world everythingmicroscopescan be divided:

1. Educational microscopes. They are also called school or children's.
2. Digital microscopes. The main task of a digital microscope is not just to show an object in an enlarged form, but also to take a photograph or shoot a video.
3. Laboratory microscopes. The main task of a laboratory microscope is to conduct specific research in various fields of science, industry, and medicine.

Making your own microscope

When we were looking for information about the history of microscopes, we learned on one of the sites that you can make your own microscope from a drop of water. And then I decided to try to conduct an experiment to create such a microscope. You can make a small microscope from a drop of water. To do this, you need to take thick paper, pierce a hole in it with a thick needle and carefully place a drop of water on it. The microscope is ready! Bring this droplet to the newspaper - the letters become larger. How less drop, the greater the increase. In the first microscope invented by Leeuwenhoek, everything was done exactly like this, only the droplet was glass.

We found a book called “My First Scientific Experiments” and made the microscope model a little more complicated. For work I needed:

1. Glass jar.
2. Metallized paper (baking foil).
3. Scissors.
4. Scotch.
5. Thick needle.
6. Plasticine.

When I collected all this, I began to create a model of the microscope. Below I will describe all my work step by step. Of course, I needed a little help from my mom and sister.

MICROSCOPE

REPORT on Biology for a 6th grade student

For a long time, a person lived surrounded by invisible creatures, used the products of their vital activity (for example, when baking bread from sour dough, preparing wine and vinegar), suffered when these creatures caused illnesses or spoiled food supplies, but did not suspect their presence . I didn’t suspect it because I didn’t see it, and I didn’t see it because the size of these micro creatures was much lower than the limit of visibility that I was capable of. human eye. It is known that a person with normal vision at the optimal distance (25-30 cm) can distinguish an object measuring 0.07–0.08 mm in the form of a point. A person cannot notice smaller objects. This is determined by the structural features of his organ of vision.

Around the same time that space exploration began with telescopes, the first attempts were made to reveal the mysteries of the microworld using lenses. Thus, during archaeological excavations in Ancient Babylon, biconvex lenses were found - the simplest optical instruments. The lenses were made from polished rock crystal We can consider that with their invention, man took the first step on the path to the microworld.

The easiest way to enlarge the image of a small object is to observe it with a magnifying glass. A magnifying glass is a converging lens with a small focal length (usually no more than 10 cm) inserted into the handle.

Telescope creator Galileo V 1610 year, he discovered that when greatly extended, his telescope made it possible to greatly magnify small objects. It can be considered inventor of the microscope consisting of positive and negative lenses.
A more advanced tool for observing microscopic objects is simple microscope. It is not known exactly when these devices appeared. At the very beginning of the 17th century, several such microscopes were made by a spectacle maker. Zachariah Jansen from Middelburg.

In the essay A. Kircher, published in 1646 year, contains a description a simple microscope named by him "flea glass". It consisted of a magnifying glass embedded in a copper base, on which an object table was mounted, which served to place the object in question; at the bottom there was a flat or concave mirror that reflected the sun's rays onto the object and thus illuminated it from below. The magnifying glass was moved by means of a screw to the stage until the image became clear and distinct.

First outstanding discoveries were made just using a simple microscope. In the middle of the 17th century, the Dutch naturalist achieved brilliant success Anthony Van Leeuwenhoek. Over the years, Leeuwenhoek perfected his ability to make tiny (sometimes less than 1 mm in diameter) biconvex lenses, which he made from a small glass ball, in turn obtained by melting a glass rod in a flame. This glass bead was then ground using a primitive grinding machine. Throughout his life, Leeuwenhoek made at least 400 such microscopes. One of them, kept in the University Museum in Utrecht, gives more than 300 times magnification, which was a huge success for the 17th century.

At the beginning of the 17th century there appeared compound microscopes, composed of two lenses. The inventor of such a complex microscope is not exactly known, but many facts indicate that he was a Dutchman Cornelius Drebel, who lived in London and was in the service of the English King James I. In a compound microscope there was two glasses: one - the lens - facing the object, the other - the eyepiece - facing the eye of the observer. In the first microscopes, the lens was a biconvex glass, which gave a real, magnified, but inverted image. This image was examined with the help of an eyepiece, which thus played the role of a magnifying glass, but only this magnifying glass served to enlarge not the object itself, but its image.

IN 1663 year microscope Drebel was improved English physicist Robert Hooke, who introduced a third lens into it, called the collective. This type of microscope gained great popularity, and most microscopes of the late 17th - first half of the 8th century were built according to its design.

Microscope device

A microscope is an optical instrument designed to examine magnified images of micro-objects that are invisible to the naked eye.

Main parts light microscope(Fig. 1) are a lens and an eyepiece enclosed in a cylindrical body - a tube. Most models intended for biological research are equipped with three lenses with different focal lengths and a rotating mechanism designed for their quick change - a turret, often called a turret. The tube is located on the top of a massive tripod, which includes a tube holder. Just below the lens (or a turret with several lenses) there is a stage on which slides with the samples under study are mounted. Sharpness is adjusted using the coarse and fine adjustment screw, which allows you to change the position of the stage relative to the lens.

In order for the sample under study to have sufficient brightness for comfortable observation, microscopes are equipped with two more optical units (Fig. 2) - an illuminator and a condenser. The illuminator creates a stream of light that illuminates the drug being studied. In classical light microscopes, the design of the illuminator (built-in or external) involves a low-voltage lamp with a thick filament, a collecting lens and a diaphragm that changes the diameter of the light spot on the sample. The condenser, which is a collecting lens, is designed to focus the illuminator beams on the sample. The condenser also has an iris diaphragm (field and aperture), with which the light intensity is adjusted.

When working with objects that transmit light (liquids, thin sections of plants, etc.), they are illuminated with transmitted light - the illuminator and condenser are located under the object stage. Opaque samples need to be illuminated from the front. To do this, the illuminator is placed above the object stage, and its rays are directed to the object through the lens using a translucent mirror.

The illuminator can be passive, active (lamp) or consist of both elements. The simplest microscopes do not have lamps to illuminate samples. Under the table they have a two-way mirror, one side of which is flat and the other is concave. In daylight, if the microscope is placed near a window, you can get pretty good illumination using a concave mirror. If the microscope is located in a dark room, a flat mirror and an external illuminator are used for illumination.

The magnification of a microscope is equal to the product of the magnification of the objective and the eyepiece. With an eyepiece magnification of 10 and an objective magnification of 40, the total magnification factor is 400. Typically, a research microscope kit includes objectives with a magnification of 4 to 100. A typical set of microscope lenses for amateur and educational research(x 4, x10 and x 40), provides an increase from 40 to 400.

Resolution is another important characteristic of a microscope, determining its quality and clarity of the image it forms. The higher the resolution, the more small details can be seen when high magnification. In connection with resolution, they talk about “useful” and “useless” magnification. “Useful” is the maximum magnification at which maximum image detail is provided. Further magnification (“useless”) is not supported by the resolution of the microscope and does not reveal new details, but can negatively affect the clarity and contrast of the image. Thus, the useful magnification limit of a light microscope is not limited overall coefficient the magnification of the lens and eyepiece - it can be made as large as desired - but by the quality of the optical components of the microscope, that is, resolution.

The microscope includes three main functional parts:

1. Lighting part
Designed to create a light flux that allows you to illuminate an object in such a way that subsequent parts of the microscope perform their functions with utmost precision. The illuminating part of a transmitted light microscope is located behind the object under the lens in direct microscopes and in front of the object above the lens in inverted microscopes.
The lighting part includes a light source (lamp and electrical power supply) and an optical-mechanical system (collector, condenser, field and aperture adjustable/iris diaphragms).

2. Reproducing part
Designed to reproduce an object in the image plane with the image quality and magnification required for research (i.e., to construct an image that would reproduce the object as accurately as possible and in all details with the resolution, magnification, contrast and color rendition corresponding to the microscope optics).
The reproducing part provides the first stage of magnification and is located after the object to the microscope image plane. The reproducing part includes a lens and an intermediate optical system.
Modern microscopes the latest generation are based on optical lens systems corrected for infinity.
This additionally requires the use of so-called tube systems, which “collect” parallel beams of light emerging from the lens in the microscope image plane.

3. Visualization part
Designed to obtain a real image of an object on the retina, photographic film or plate, on the screen of a television or computer monitor with additional magnification (second magnification stage).

The visualizing part is located between the image plane of the lens and the eyes of the observer (camera, photo camera).
The imaging part includes a monocular, binocular or trinocular imaging head with an observation system (eyepieces that work like a magnifying glass).
In addition, this part includes additional magnification systems (magnification wholesaler/change systems); projection attachments, including discussion attachments for two or more observers; drawing apparatus; image analysis and documentation systems with corresponding matching elements (photo channel).