Optical phenomena (physics, 8 class). Atmospheric optical phenomenon. Optical phenomena and devices

Long since mirages, flickering figures in the air environment have alarmed and terrified people. Nowadays, scientists have uncovered many secrets of nature, including optical phenomena. They are not surprised by natural riddles, the essence of which has long been studied. In the secondary school, optical phenomena in physics in the 8th class are held today, so that any student can understand their nature.

Basic concepts

Scientists of antiquity believed that the human eye sees thanks to the feeling of objects with the finest tentacles. Optics at the time was a doctrine of vision.

In the Middle Ages, optics studied the light and its essence.

Today, optics is a part of physics that studies the propagation of light in a variety of media and its interaction with other substances. All questions concerning vision are studied by physiological optics.

Optical phenomena are manifestations of various actions performed by the rays of light. They are studied by atmospheric optics.

Unusual processes in the atmosphere

The planet Earth is surrounded by a gas shell called the atmosphere. Its thickness is hundreds of kilometers. Closer to the Earth, the atmosphere is more dense, in the direction upwards it is rarefied. The physical properties of the atmospheric envelope are constantly changing, the layers are mixed. Change the temperature. Density, degree of transparency shift.

From the sun and other celestial bodies towards the Earth go light rays. They pass through the atmosphere of the Earth, which for them serves as a specific optical system, changing its characteristics. The light rays are reflected, scattered, pass through the atmosphere, illuminate the earth. Under certain conditions, the path of the rays curves, so various phenomena arise. The most original optical phenomena of physics are:

• Sunset of the sun;
• The appearance of the rainbow;
• Northern Lights;
• mirage;
• halo.

Let us consider them in more detail.

Halo around the Sun

The very word "halo" in Greek means "circle". What is the optical phenomenon in its basis?

The halo is the process of refraction and reflection of rays, arising in cloud crystals high in the atmosphere. The phenomenon looks like glowing rays near the Sun, bounded by a dark interval. Usually halos are formed before cyclones and can be their harbingers.

Water drops freeze in the air and take the correct prismatic shape with six sides. Everyone is familiar with icicles that appear in the lower atmospheric layers. Above, such icy needles freely descend in a vertical direction. Crystal ice floes, descend to the ground, while they have a parallel arrangement with respect to the ground. Man directs sight through crystals that act as lenses and refract light.

Other prisms turn out to be flat or they look like stars with six rays. The rays of light, falling on the crystals, can not be refracted or experience a number of other processes. It rarely happens that all processes are clearly visible, usually one or another part of the phenomenon is more pronounced, while others are poorly represented.

A small halo is a circle around the sun with a radius of about 22 degrees. The color of the circle is reddish from the inside, then flows into yellow, white and blends with the blue sky. The inner area of the circle is dark. It is formed as a result of refraction in the needles of ice flying in the air. The rays in the prisms deflect at an angle of 22 degrees, so those of them that passed through the crystals are shown to the observer by 22 degrees. Therefore, the interior space appears to be dark.

Red color refracts less, shows the least deviation from the sun. Then follows the yellow. The other rays are mixed and appear white.

There is a halo with an angle of 46 degrees, it is located around the halo at 22 degrees. Its internal area is also reddish, because the light undergoes refraction in ice needles turned to the sun by 90 degrees.

A 90-degree halo is also known, it glows slightly, has almost no color or is colored red from the outside. Scientists have not yet fully studied this species.

Halo around the Moon and other species

This optical phenomenon is often seen if there are light clouds and a lot of miniature crystal ice in the sky. Each such crystal is a kind of prism. In general, their shape is elongated hexahedrons. Light enters the front crystalline region and, going into the opposite part, refracts by 22 degrees.

In winter, around the street lamps in the cold air you can see the halo. It appears because of the light of the lantern.

Around the Sun, a halo can form in the frosty snow-covered air. Snowflakes are floating in the air, light passes through the clouds. In the evening sunset, this light turns red. In past centuries superstitious people were horrified by such phenomena.

The halo can look like a circle of rainbow color around the Sun. It appears if there are many crystals with six facets in the atmosphere, but they do not reflect, but refract the rays of the sun. Most of the rays are scattered, not reaching our gaze. The remaining rays reach the human eyes, and we notice the iridescent circle around the Sun. Its radius is about 22 degrees or 46 degrees.

The False Sun

Scientists noted that the halo circle is always brighter on the sides. This is due to the fact that there are vertical and horizontal halos. In places where they intersect, false suns may appear. Especially often it happens when the Sun is near the horizon, at this time part of the vertical circle, we can not see.

The false sun is also an optical phenomenon, a kind of halo. It appears because of the ice crystals with six faces, which have a shape resembling nails. Such crystals are in the atmosphere in the vertical direction, light is refracted in their lateral faces.

A third "sun" can also form, if only the surface part of the halo circle is visible above the true sun. It can be a segment of an arc or a glowing spot of an incomprehensible shape. Sometimes false suns are so bright that they can not be distinguished from the real Sun.

Rainbow

This is an atmospheric optical phenomenon in the form of an incomplete circle with different colors.

The religions of antiquity considered the rainbow to be a bridge from heaven to earth. Aristotle believed that the rainbow appears because of the reflection of drops of sunlight. What optical phenomenon is still capable of making a person happy, like a rainbow does?

In the XVII century, Descartes studied the nature of the rainbow. Later Newton experimented with light and supplemented Descartes' theory, but could not understand the formation of several rainbows, the absence of separate color shades in them.

The full theory of rainbow was presented in the XIX century by an astronomer from England D. Erie. It was he who managed to uncover all the processes of the rainbow. The theory developed by him is accepted even today.

The rainbow appears when the sun's light hits the veil of rainwater in the area of the sky, back from the Sun. The center of the rainbow is located at the point on the other side of the Sun, that is, it is not visible to the eye of a person. The rainbow arc is part of the circle around this central point.

Colors in the rainbow are placed in a certain order. He is constant. Red - on the top edge, purple - on the bottom. Between them the colors go in strict alignment. In the rainbow are not all the existing colors. The predominance of green color indicates a transition to favorable weather.

Polar Lights

This glow in the upper magnetic layers of the atmosphere due to the interaction of atoms and elements of the solar wind. Usually the auroras have green or blue shades with pink and red inclusions. They can take the form of a tape or stain. Their outbursts are often accompanied by noisy sounds.

Mirage

Simple mirage deceptions are familiar to any person. For example, when driving on a heated asphalt a mirage appears as a water surface. It's no one's surprise. What optical phenomenon explains the appearance of mirages? Let us dwell on this issue in more detail.

Mirage is an optical physical phenomenon in the atmosphere, as a result of which the eye sees objects hidden from view under normal conditions. This is due to the refraction of the light beam as it passes through the air layers. Objects that are at a significant distance, while they can rise or fall relative to their true location, and can distort and acquire bizarre outlines.

Brocken's ghost

This is a phenomenon in which the shadow of a person on an elevation acquires an inconceivable scale at sunset or sunrise of the sunlight, as it falls on clouds that are nearby. This is due to the reflection and refraction of light rays by water droplets in foggy conditions. The phenomenon was named after one of the heights of the German Harz Mountains.

The Lights of St. Elmah

These are luminous brushes of blue or violet color on the masts of sea ships. Lights can appear on mountain heights, on buildings of impressive height. This phenomenon arises due to the electrical discharges at the ends of the conductors due to the fact that the electrical tension increases.

These are the optical phenomena considered in class 8 lessons. Let's talk about the devices of optics.

Constructions in optics

Optical devices are devices that convert light. Usually these devices work in visible light.

All optical devices can be divided into two types:

1. Devices, in which the image is obtained on the screen. These are cameras, cameras, projection devices.
2. Devices that interact with the human eye, but do not form images on the screen. This is a magnifying glass, a microscope, and telescopes. These devices are considered to be visual.

A camera is an optical-mechanical device used to obtain images of an object on a photographic film. The design of the camera includes a camera and lenses forming an objective. The lens creates an inverted, reduced image of the object, fixed on the film. This is due to the action of light.

The image is invisible at first, but, thanks to the developing solution, becomes visible. This image is called a negative, in it the bright places look dark, and vice versa. From the negative, a positive is done on the photosensitive paper. Using a magnifier, the image is enlarged.

A magnifier is a lens or a lens system designed to magnify objects in the process of viewing them. Lupu is located next to the eye, select the distance from which the object appears clearly. The application of the magnifier is based on the increase in the angle of view under which the subject is examined.

To obtain a larger angular magnification, use a microscope. In this device, the magnification of objects is due to an optical system consisting of an objective and an eyepiece. First, the angle of view is increased by the lens, then - by the eyepiece.

So, we examined the main optical phenomena and devices, their varieties and features.