Checking homework.

1. What vibrations are called ultrasonic?

a) mechanical vibrations, the frequencies of which are higher 20000 Hz;

b) mechanical vibrations with a frequency above 16 Hz;

c) mechanical vibrations, the frequencies of which lie in the range from 16 to 20,000 Hz.

2. Can sound waves propagate in vacuum?

a) can, for example, the sound of a shot in a vacuum;

b) cannot: sound waves propagate only in matter;

c) they can, if the sound waves are transverse.

3. What quantities does the pitch depend on?

a) on the amplitude;

b) on frequency;

c) from loudness;

d) on the speed of sound propagation.

4. How does sound propagate in a homogeneous medium?

a) sound travels in a straight line at a constant speed in one direction;

b) sound propagates in all directions, the speed decreases with distance;

in) Sound travels in a straight line and at a constant speed in all directions.

5. What determines the speed of sound in air? a) from the volume of the sound;

b) on the pitch of the sound;

c) on temperature;

d) on the speed of the sound source.

6. What determines the pitch of the sound?

a) on the amplitude of oscillations;

b) on the wavelength;

c) on the vibration frequency of the sound source.

7. What is infrasound?

a) fluctuations below 16 Hz;

b) fluctuations above 16 Hz;

c) fluctuations above 20,000 Hz.

8. Transverse elastic waves are possible: a) only in solids;

b) only in gases;

c) in gases, solids and liquids.

lesson topic:"Reflection of sound. Echo".

Without a body - but it lives, Without a language - screams!.......

Echoes are sound waves reflected from an obstacle and returning to their source.

The name "echo" is associated with the name of the mountain nymph Echo

The ancient Greeks came up with a very beautiful legend to explain the echo. Long ago, there lived a beautiful nymph named Echo. She had only one drawback - she talked too much. As punishment, the goddess Hera forbade her to speak unless spoken to. The nymph could only repeat what she was told. One day, Echo saw a handsome young Narcissus and immediately fell in love with him. However, Narcissus did not notice her. The nymph was seized with such sadness that Echo vanished into thin air, leaving only her voice. And we hear her voice, which repeats everything we say.

echo formation

The echo is formed as a result of the reflection of sound from various obstacles - the walls of a large empty room, a forest, the vaults of a high arch in a building. We hear an echo only when the reflected sound is perceived separately from the spoken one. To do this, it is necessary that the time interval between the impact of these two sounds on the ear eardrum be at least 0.06 s.

Echo in the mountains

The most amazing echo "lives" in the mountains. There it is repeated many times, as a result of repeated reflection of sound.

What is an echo like?

Echo is of several types:

once e is the wave reflected from the obstacle and received by the observer.

2) Multiple - this is an echo that occurs at some loud sound, which gives rise to not one, but several successive sound responses.

cons of echo

The big disadvantage of echo is that it is a significant hindrance to audio recording. Therefore, the walls of the rooms in which songs are recorded, radio reports are usually equipped with sound-damping screens made of soft or ribbed materials that absorb sound.

Styrofoam

echo application

Since sound waves in air have a constant propagation speed (about 340 meters per second), the time it takes for the sound to return can serve as a source of data on the removal of an object.

1. Acoustic echo is used in sonar, as well as in navigation, where echo sounders are used to measure the depth of the bottom.

2) ultrasonic flaw detection(detection of defects, cavities, cracks in cast metal products),

3) echo research in medicine

Famous echoes of the world

At Woodstock Castle 17 syllables(destroyed during the Civil War).

Ruins Derenburg Castle near Halberstadt gave 27-difficult an echo that, however, has been silenced since one wall was blown up.

rocks spread out in a circle near Adersbach in Czechoslovakia, repeat, in a certain place, triple 7 syllables; but a few steps from this point, even the sound of a gunshot does not give any echo.

A very multiple echo was observed in one (now defunct) castle near Milan : shot, produced from the window of the wing, echoed 40 - 50 times, a big word - times 30 .

At Woodstock Castle in England the echo distinctly repeated 17 syllables(destroyed during the Civil

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Contents Who are they? Family Dolphins are excellent swimmers Echolocation Social life Preparing for childbirth Chatterboxes and naughty people Representatives

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What are they? Dolphins are aquatic mammals, the dolphin family of the suborder of toothed whales; includes about 20 genera, about 50 species: sotalia, stenella, common dolphins, whale dolphins, short-headed dolphins, beak-headed dolphins, bottlenose dolphins (two species), gray dolphins, black killer whales, pilot whales, killer whales, porpoises, white-winged porpoises, featherless porpoises , comb-toothed dolphins (Steno bredanensis). Some can be found in any ocean. Many consider them intelligent beings seeking to communicate with humans.

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The length of dolphins is 1.2-10 m. Most have a dorsal fin, the muzzle is extended into a “beak”, and there are numerous teeth (more than 70). Dolphins are often kept in dolphinariums where they can breed. Dolphins have very large brains. They have a memory and an amazing ability to imitate and adapt. They are easy to train; capable of sound reproduction. The hydrodynamic perfection of body shapes, the structure of the skin, the hydroelastic effect of the fins, the ability to dive to a considerable depth, the reliability of the sonar, and other features of dolphins are of interest to bionics. One species of dolphins is listed in the International Red Book.

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Dolphin family DOLPHIN (dolphins; Delphinidae) - a family of marine mammals of the suborder of toothed whales; includes two subfamilies: narwhals (beluga and narwhal) and dolphins, which are sometimes considered as separate families. Often among the dolphins, a subfamily of porpoises is distinguished. The family includes small (1-10 m), predominantly mobile marine cetaceans of a slender build.

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Dolphins are excellent swimmers. Their speed of movement can reach 55 km/h. Sometimes they use the waves from the bow of the ship to move even faster and use less energy. At the top of the head, dolphins have a nostril, called a blowhole, through which they ventilate their lungs. Dolphins' eyes see just as well on the surface as they see underwater. A thick layer of fat is located under the skin, protects them from cold and heat, and also serves as a store of nutrients and energy. The pad of fat covering the top of the dolphin's head gives these animals a permanent smile. The skin of dolphins is extremely soft and elastic. It dampens the turbulence of the water around when moving and allows you to swim faster.

Slide 7

Echolocation Dolphins have a natural resemblance to ultrasonic radar or sonar. It is located in their head and makes it easy to detect prey, obstacles and dangers, accurately determining the distance to them. This radar also serves as a compass. When it "goes wrong", dolphins can be washed ashore. Dolphins have tiny ears, but they pick up most of the sounds with the lower jaw, along the nerves of which these signals are transmitted to the brain.

Slide 8

Social life Dolphins live in groups. The smallest herds number 6-20 individuals, the largest - more than 1000. The leader of the group, the oldest dolphin, leads the herd with the help of several males, whom he sends ahead as scouts. Dolphins always help each other and rush to the rescue as soon as one of them is in trouble. They usually elude killer whales trying to surround them and attack sharks that pose a danger to them.

Slide 9

Preparing for childbirth Pregnancy of the female lasts 10-16 months, depending on the type of dolphin. Before giving birth, she swims away from the group, accompanied by an older female (“godmother”), who will help her during childbirth and look after the baby while the mother gets food. The baby is born tail first. To become an adult, he will need from 5 to 15 years

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Chatterboxes and naughty Dolphins are excellent acrobats. They communicate with each other by jumping, as well as the language of whistling, clicking and squeaking. Each dolphin has an individual voice, and each group has its own language.

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River dolphins A family of aquatic mammals of the suborder of toothed whales; includes 5–6 species found in the rivers of South Asia and South America, as well as in the Atlantic Ocean off the coast of South America. This is the oldest family of the suborder, which arose in the Miocene. The length of river dolphins is up to 3 m. The pectoral fins are short and wide, instead of the dorsal fin there is a low elongated crest. River dolphins feed on fish, shellfish and worms. In the rivers of South America, there is an Amazonian inia. The Gangetic dolphin is common in the rivers of India and Pakistan - the Ganges, the Brahmaputra and the Indus. The Indian dolphin (Platanista Indi) is close to it.

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BEAKED DOLPHINS (variegated dolphins, Serhalorhynchus) - a genus of marine animals of the dolphin subfamily; small (120-180 cm long) variegated animals of the temperate waters of the Southern Hemisphere. The beak is not pronounced, as it imperceptibly passes into the head. Mouth small, dorsal fin rounded or slightly pointed at apex. The color of the body is combined from white and dark tones; all fins are black. Teeth small, conical, 25-31 in each row. There are at least four species in the genus.

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SHORT-HEADED DOLPHINS A genus of marine animals of the dolphin subfamily; unites animals, the size of which is not more than 3 m. Their head is shortened, the beak is short, barely delimited from the fronto-nasal pillow. The large dorsal fin on the posterior margin is crescent-shaped, so deep that its apex points straight back. Pectoral fins of moderate size. The upper and lower edges of the caudal peduncle are high, in the form of ridges. The coloration of most species is bright, of contrasting black and white tones. A dark stripe runs from the base of the pectoral fin to the eye. Teeth numerous, 22-40 pairs above and below, 3-7 mm thick. The palate is flat. Short-headed dolphins are characterized by an increased number of vertebrae. The genus unites six species living in the temperate and warm temperate waters of the World Ocean; some of them go to the outskirts of the Antarctic and the Arctic.

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WHALE DOLPHINS A genus of marine animals of the dolphin subfamily; they are distinguished by a thin and slender body 185-240 cm long without a dorsal fin, a moderately long pointed beak, which is smoothly demarcated from a low, sloping frontal fat pad. The pectoral fins are crescent-shaped, small, convex along the lower edge, concave along the upper edge. The tail stalk is thin and low. The teeth are small, about 3 mm thick, 42-47 pairs at the top and 44-49 pairs at the bottom. The sky is flat, without grooves. There are two rare species in the genus - the northern right whale dolphin and the southern right whale dolphin.

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ATLANTIC WHITE-SIDED DOLPHIN Species of a marine animal of the genus of short-headed dolphins; body length 2.3-2.7 m. The entire upper body of this dolphin is black, the bottom from the chin to the end of the tail is white. The pectoral fins, like the dorsal, are black, attached to the light part of the body, and a black strap runs from them to the eye. An elongated white field stands out on the sides in the posterior half of the body. From above it borders on black, below - on gray. Teeth 30-40 pairs at the top and bottom, up to 4 mm thick.

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BELLOWBONK A genus of marine mammals of the dolphin family; includes two types. Length up to 2.6 m, males are slightly larger than females. The back and fins are dark, the sides are gray with white patches; long beak. Dolphins are common in warm and temperate waters, including the Black Sea; unlike the bottlenose dolphin, it prefers the open sea. Several subspecies live within Russia: the Black Sea (the smallest), the Atlantic and the Far East. Dolphins feed on schooling fish (hamsa, haddock, red mullet, herring, capelin, sardine, anchovy, hake) and cephalopods. The Black Sea subspecies feeds at a depth of up to 70 m, but the oceanic subspecies dive to a depth of 250 m.

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bottlenose dolphin Marine mammal of the dolphin family. Body length up to 3.6-3.9 m, weighs 280-400 kg. A moderately developed beak is clearly demarcated from a convex fronto-nasal pad, the color of the body is dark brown above, light (from gray to white) below; the pattern on the sides of the body is not constant, often not at all pronounced. Teeth strong, conically pointed. The bottlenose dolphin is widely distributed in temperate and warm waters, including the Black, Baltic and Far Eastern seas. There are four subspecies in the oceans: Black Sea, Atlantic, North Pacific, Indian (which is sometimes distinguished as an independent species). The bottlenose dolphin can reach speeds of up to 40 km/h and jump out of the water to a height of up to 5 m.

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Grinds Genus of marine mammals of the dolphin subfamily; includes three types. The length of pilot whales is up to 6.5 m, weight is up to 2 tons. They are distinguished by a spherically rounded head, almost devoid of a beak. Narrow and long pectoral fins set low. The dorsal fin is bent back and shifted to the anterior half of the body. Pilot whales are widely distributed (excluding the polar seas), they are an object of fishing in the northern part of the Atlantic Ocean. The best studied is the common pilot whale. She is almost all black, on her belly there is a white pattern in the form of an anchor. She has a highly developed herd instinct and the instinct to preserve the species. It is capable of speeds up to 40 km/h.

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Killer Whale The only species of the eponymous genus of marine mammals of the dolphin subfamily. Length up to 10 m, weight up to 8 tons. The head is moderate in size, wide, slightly flattened from above, equipped with powerful chewing muscles. The fronto-nasal pad is low, the beak is not pronounced. All fins are greatly enlarged, especially the dorsal (up to 1.7 m in old males). The teeth are massive, 10-13 pairs at the top and bottom. The body is black from above and from the sides, an oval spot above each eye, a light saddle behind the dorsal fin (females do not have). The white color of the throat on the belly turns into a stripe. A variety of sound signals: from high tones to groans and screams play an important communication role: they warn of danger, call for help, etc. They can move at speeds up to 55 km / h.

Echolocation (film). Ultrasound is widely used in technology. For example, directed narrow beams of ultrasound are used to measure the depth of the sea. For this purpose, an ultrasound emitter and receiver are placed on the bottom of the vessel. The emitter gives short signals that reach the bottom and, reflected from it, reach the receiver. Sea depth formula: vt. h=. 2.

Slide 8 from the presentation « physical characteristics sound". The size of the archive with the presentation is 1088 KB.

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Sound reflection. Echo.

MOU secondary school No. 66, Magnitogorsk

Shcherbakova Yu.V.

Physics teacher

Repetition, checking homework.

1. What are oscillations? What kind

Do you know the types of oscillations?

2. What are the magnitudes of fluctuations?

3. What are called waves? What types of waves do you know?

4. In what medium can longitudinal and transverse waves propagate and why?

5. What is the formula for calculating wavelength?

6. Give examples of natural

sound sources and artificial.

How common property possess

all sound sources?

7. Fluctuations of what range are called sound? ultrasonic? infrasonic?

8. Swing sound

flying wings

we hear a mosquito

but flying

birds are not. Why?

10. Tell us about the experience shown in the picture. What conclusion can be drawn from this experience?

Why do we not hear the roar of powerful processes occurring on the Sun?

9. Tell us about measuring the depth of the sea using echolocation.

Topic:

"Reflection of sound. Echo."

Anchoring

1. At what distance is the obstacle from the person if the sound signal sent by him was received after 3 seconds? The speed of sound in air is 340m/s.

2. The thickness of the steel plate is 4 cm. The product is examined using an ultrasonic flaw detector. The reflected signal arrived at one place after 16 μs. And in another place - after 12 microseconds. Is there a defect in the plate? If yes, what size is it?

1. The sound must travel twice the distance - to the obstacle and back

Answer: 510 m

2. The difference in signal transit time can be used to judge the presence of a defect. The signal must travel twice the distance to the end of the plate or defect and back.

S 1 =V*t 1 /2S 2 =V*t 2 /2 S=S 1 -S 2

Answer: 1 cm

Questions:

1. What causes an echo?

2. Why doesn't echo occur in a small room full of furniture?

3. How can the sound properties of a large hall be improved?

4. Why does sound travel a greater distance when using a horn?

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Echolocation Dolphins have a natural resemblance to ultrasonic radar or sonar. It is located in their head and makes it easy to detect prey, obstacles and dangers, accurately determining the distance to them. This radar also serves as a compass. When it goes wrong, dolphins can be washed ashore. Dolphins have tiny ears, but they pick up most of the sounds with the lower jaw, along the nerves of which these signals are transmitted to the brain.

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River dolphins A family of aquatic mammals of the suborder of toothed whales; includes 5–6 species living in the rivers of South Asia and South America, as well as in the Atlantic Ocean off the coast of South America. This is the oldest family of the suborder, which arose in the Miocene. The length of river dolphins is up to 3 m. The pectoral fins are short and wide, instead of the dorsal fin there is a low elongated crest. River dolphins feed on fish, shellfish and worms. In the rivers of South America, there is an Amazonian inia. The Gangetic dolphin is common in the rivers of India and Pakistan - the Ganges, the Brahmaputra and the Indus. The Indian dolphin (Platanista Indi) is close to it.

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bottlenose dolphin Marine mammal of the dolphin family. Body length up to 3.6-3.9 m, weighs 280-400 kg. A moderately developed beak is clearly demarcated from a convex fronto-nasal pad, the color of the body is dark brown above, light (from gray to white) below; the pattern on the sides of the body is not constant, often not at all pronounced. The teeth are strong, conically pointed. The bottlenose dolphin is widely distributed in temperate and warm waters, including the Black, Baltic and Far Eastern seas. There are four subspecies in the oceans: Black Sea, Atlantic, North Pacific, Indian (which is sometimes distinguished as an independent species). The bottlenose dolphin can reach speeds of up to 40 km/h and jump out of the water to a height of up to 5 m.

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Grinds Genus of marine mammals of the dolphin subfamily; includes three types. The length of pilot whales is up to 6.5 m, weight is up to 2 tons. They are distinguished by a spherically rounded head, almost devoid of a beak. Narrow and long pectoral fins set low. The dorsal fin is bent back and shifted to the front half of the body. Pilot whales are widely distributed (excluding the polar seas), they are an object of fishing in the northern part of the Atlantic Ocean. The best studied is the common pilot whale. She is almost all black, on her belly there is a white pattern in the form of an anchor. She has a highly developed herd instinct and the instinct to preserve the species. It is capable of speeds up to 40 km/h.

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