verification of laws of reflection of sound experiment

Verify the Laws of Reflection of Sound | Science Experiment

by Cisco Ramon | Nov 9, 2021 | Electronics Experiments , Experiments , Physics Experiments

Introduction

In this Science Experiment, we will see how we can verify the laws of reflection of sound.

First of all, we should know what sound is. Let us take a quick review of it.

1. We hear different types of voices in our daily lives, whether living or nonliving. These voices are called sounds. 2. The material in which sounds travel is called medium. 3. Medium can be solid, liquid or gas. 4. Sound is produced when vibrating objects hit each other in the medium. 5. In sound, one form of energy is converted into another form of energy. For example, clapping of hands- in this, the kinetic energy turns into sound energy.

1. Wave is a disturbance produced in a medium when one particle in motion sets its neighbouring particle into motion. 2. Particles do not move from one point to another; instead, they create a disturbance. And this is what happens in sound. 3. Therefore, sound can also be imagined as a wave. 4. Sound wave is a longitudinal wave, i.e. the particles move along the direction of propagation of disturbance.

Note: Particles do not move from one point to another. They just set neighbouring particles in motion while oscillating in their mean position.

Characteristics of A Sound Wave

1. Compression: It is the area where particles are crowded. The density and pressure in this area are high. The upper portion is called the crest. 2. Rarefaction: This is the area where particles are separated from each other. The density, as well as pressure in this region, is low. The lower portion is called the trough. 3. Wavelength: It represents the distance between two troughs and two crests. It is denoted by the Greek letter ⋋. 4. Frequency: It is the number of oscillations per unit time represented by v. 5. Time period: It is the time taken to complete one revolution in the medium. 6. Amplitude: The softness and hardness are determined by amplitude. It is the distance moved by an object in the medium. 7. Pitch: Pitch depends on frequency, i.e. faster the vibration of sound in a medium, the greater will be the frequency and the higher will be the pitch. 8. Speed: It is the distance travel in compression or refraction per unit time.

Speed of Sound in Different Medium

1. Speed of sound is less than the speed of light. 2. Depends on the properties of the medium through which it travels. 3. Directly proportional to the temperature of the medium through which it travels. 4. Speed of sound decreases while going from denser medium to rarer medium. 5. Speed of sound in air is 343 m/sec, water is 1437m/sec, and wood is 3850m/sec.

Reflection of Sound

Like light, sound also reflects after hitting a surface. It follows the same law of reflection i.e.

1. Angle of incidence and angle of reflection with the normal is equal. 2. Incident sound, reflected sound and normal all lie in the same plane.

Aim of the Experiment

To verify the laws of reflection of sound.  

Requirements

1. Stopwatch 2. Two hollow cardboard cylindrical sheets 3. Glass slab 4. Drawing board 5. White sheet 6. Drawing pins 7. Cardboard

When sound bounces back after hitting any surface, it is called a reflection of sound.

The laws of reflection of sounds are:-

1. Angle of incidence and angle of reflection with the normal is equal. 2. Incident sound, reflected sound and normal all lie in the same plane

Step 1: Attach a white sheet on the drawing board with the help of drawing pins.

Step 2: Draw a line AB at the one edge of a white sheet.

Step 3: Take a point C on it and draw a normal CD through it.

Step 4: Draw an angle of 30 degrees, taking a point E so that <ECD= 30°

Step 5: Place the glass slab on line XY.

Step 6: Place cardboard along the normal CD.

Step 7: Place two pieces of cardboard making an angle of  30° with the normal. See the figure below.

Step 8: Place a clock at the end of one of the cardboard.

Step 9: Try listening to the sound of the clock through other cardboard. When you find the position of clear sound, mark that position as point F.

Step 10: Try to hear the sound of the clock by lifting CF to a small height.

Step 11: Now, lift the glass slab, tubes and screen.

Step 12: Join the point CF and measure the <DCF, and note it.

Step 13: Try this process by taking different angles.

Observation

The sound would be decreased when you uplift the end of tube CF.

From this experiment, we have seen that apart from error, the angle of incidence and the angle of reflection of sound is equal. And all the incident sound reflected sound and normal lie on the same plane.

Precautions

1. Glass slab should be clean. 2. Mark the tube’s position immediately after hearing the maximum and clear sound of the clock. 3. Reflecting surface should be placed vertically. 4. Angle should be measured between cardboard and tube. 5. Glass slab, ear and stopwatch all should lie on the same plane.

In this experiment, we have learned how we can verify the laws of reflection of sound.

Viva Questions With Answers

Q.1 Why do you hear your voice in an empty room?

Ans. Because the walls of the empty room reflect the sound produced by me.

Q.2 What is the SI unit of frequency?

Q.3 What is the time interval between original and reflected sound?

Ans. 0.1 sec

Q.4  Why it is required to use a sound source with low amplitude.

Ans. So that we could hear the sound clearly through cardboard. If we have taken a sound source of high amplitude, then we hear the sound directly in our ear.

Q.5 How can we make the sound more clear?

Ans. By painting black inside the surface of cardboard or making it rough by placing newspaper inside it.

Q.6 What happens when the same experiment is done in water?

Ans. The speed of sound in air is 343 m/sec at 20°C, and in water is 1437m/sec. So we will hear the sound faster in water than the sound we hear in the air.

An Indian physicist and astronomer.

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CBSE Class 9 Science Practical Skills – Sound

Basic Building Concepts The important experience in our everyday life is the sensory experience, for this we are equipped with ears for the detection of sound. Basically, all types of sounds which we experience are created by vibrating objects and propagate through a material medium as a wave, i.e. a medium transports the mechanical energy created by the vibrating particle from one point to another without shifting the material particles of the medium. For human beings, the range of hearing is limited to frequencies 20Hz to 20kHz, whereas a dog can perceive vibration higher than 20 kHz, i.e. upto 45000 Hz.

You can also Download Class 9 Science Notes PDF to help you to revise complete Syllabus and score more marks in your examinations.

Wave The continuous disturbance which travels through a medium, transporting the energy from one point of the medium (i.e., the point where the disturbance is created) to the other point without being shifted the material is called a wave.

Nature of Sound Wave Sound waves are the longitudinal waves because the vibration of the particle in a medium is parallel to the direction of propagation of the wave. As a result compression and rarefaction regions are formed. These involve changes in volume and density of the medium. Compression: The regions where the particles of the medium become closer during vibration, i.e. high pressure regions are called compressions. Rarefaction: The regions where the particles of the medium are farther apart from each other, i.e. low pressure regions are called rarefactions.

Characteristics of Wave Motion

• Only the disturbance created by the source in a medium travels through the medium. Medium does not move as a whole.
• Only energy is transported from one point to another point in a medium.
• There is no transfer of the matter through the medium.
• Particles of the medium do not travel during the propagation of the wave from one point to another.

Characteristics of the Medium for the Propagation of the Wave

• Medium should be elastic to store the potential energy.
• Medium should possess the inertia or mass to store the kinetic energy.
• Medium should have uniform density.

Due to these properties, medium can offer an opposition to change in volume. All the media, solids, liquids and gases possess these properties. Therefore, longitudinal waves can be propagated through all of them.

Speed of Sound The speed of sound depends on the nature of the medium through which the waves pass. It is proportional to the square root of the

• ratio of the elasticity of the medium to its density
• temperature of the medium Presence of moisture increases the velocity of sound in air because the density of dry air is greater than the density of moist air. At 20 °C temperature, the speed of sound in air is approximately 343 m/s, in water, it is 1482 m/s and in steel, it is 5960 m/s. The speed of sound in air at 0 °C is 332 m/s.

Behaviour of Sound Wave At the interface of the two media, sound waves show four possible behaviours:

• Reflection(back into the same medium but in the different direction when it falls obliquely and obey the law of reflection same as in light).
• Refraction(moves into the second medium).
• Diffraction(bending around the obstacle without crossing the interface).
• Transmission(crossing the interface into the new material or obstacle).

Reflection of Sound Whenever a sound wave gets reflected from an open end, there will not be any change in the disturbance propagated in a medium, i.e. compression/rarefaction will reflect and return as a compression/rarefaction. If the waves, get reflected from a fixed or rigid support end, there will be a change in the disturbance, i.e. compression will reflect and return as a rarefaction while rarefaction will reflect and return as a compression. Thus, the disturbance which returns in the same medium but in a different direction after striking an extended surface is known as reflection of sound wave. The incident angle and reflected angle are equal. Since the wavelength of sound wave is very large as compared to the wavelength of light wave. Therefore, for reflection of sound waves:

• Extended surface is needed.
• Size of obstacle should be large.
• Surface need not necessarily be smooth or polished.
• Surface may or may not be curved.

Practical Applications of Reflection of Sound Wave The following instruments work on the principle of reflection of sound:

• Megaphones or loudspeakers have horn-shaped openings.
• Ear trumpet or hearing aid devices.
• Concave reflecting soundboards.
• Stethoscopes used by doctors.

The reflection of sound also becomes important to the design of concert halls, cinema halls and auditoriums. The walls of such building is built from materials that reflect the sound towards audience.

Aim To verify the laws of reflection of sound.

Apparatus Required One clock or watch with a quiet tick, two similar cylindrical hollow cardboard tubes of 30-50 cm length, rough or smooth sound reflecting surface, drawing board, white paper sheet, cardboard.

Theory When a sound wave falls on an extended surface or obstacle of large size, it gets bounced back into the same medium but in different direction. This phenomenon is known as reflection of sound. The laws of reflection for the sound waves are:

• The angle of incidence made by the sound waves with the normal to the reflecting surface is equal to the angle of reflection in which sound waves get reflected, i.e.∠i = ∠r.
• Fix a white plane paper on drawing board with the help of drawing pin at the four corners of white paper.
• Draw a line XY along one edge of the paper. At any point P on this line, draw a normal PN.
• Using protractor, make an incident angle of 30° with the normal PN and mark it as ∠APN.
• Place a reflecting surface, such as stiff cardboard/plywood/glass slab/mirror on a line XY in upright position with the help of stand/modeling clay.
• Place another cardboard along normal act as a screen. This does not allow the direct hearing of the ticking sound of the clock.
• Arrange two cylindrical hollow cardboard tube in such a way that their open ends come close together as shown in the figure.
• Keep a clock near the open end of the tube placed on the line AP.
• Try to listen the clear and distinct ticking sound of the clock through the other tube placed on the other side of the screen by adjusting the position of the tube. Mark this position as B. Distinct sound can be heard because sound waves get reflected from the reflecting surface.
• Lift the end B of pipe PB, vertically upward to a small height. Try to hear the sound of the table-clock now through the pipe PB.
• Lift the tubes, reflecting surface and screen. Join the points B and P and measure the angle of reflection of sound wave.

Observations

  When the end B of the pipe PB is lifted vertically upward to a small height, the sound of the table-clock is either weakened or diminished completely.

Result From the observations, we conclude that

• within experimental error limit, angle of incidence is always/approximately equal to the angle of reflection.
• the incident sound wave, reflected wave and the normal at the point of incidence all lie in the same plane. Hence the law of reflection of sound is verified.

Precautions

• Reflecting surface and screen should be held vertically on the sheet of paper.
• Position of the ticking clock should be along the axis of the hollow cylindrical tube placed along AP.
• Mark the position of the second tube only when heard sound intensity of the ticking clock is maximum.
• Ear, ticking clock and reflecting surface should be in the same plane.
• Utmost care should be taken while taking the measurement of angle. The measurement of angle, either it is incident or reflection must be taken between the axis of the tube and the normal.

Interactive Session

Question 1. What is the aim of the experiment given to you? Answer: The aim of my experiment is to verify the laws of reflection of sound.

Question 2. How can you explain the reflection phenomenon in sound? Answer: When a sound wave falls on a hard surface having a large size like wood, stiff cardboard, it bounces back into the same medium but in different direction. This phenomenon is called reflection of sound wave.

Question 3. Suppose when you shout inside an empty hall, you hear your own sound after a short time. Why is it happen? Answer: It happens because our sound is reflected from the walls of empty hall.

Question 4. Can you choose any hard and plane wooden surface which serve as a reflector of sound? Answer: Yes, any hard and plane wooden surface can serve as a reflector of sound waves.

Question 5. Why? Answer: The wavelength of sound wave is very large as compared to the wavelength of light wave.

Question 6. What is the use of wooden screen placed between the two tubes? Answer: It cuts off the direct sound from watch to ear.

Question 7. What conclusion would you draw when the axes of both the tubes are inclined equally to the normal? Answer: The angle of incidence (i) is equal to the angle of reflection (r).

Question 8. Which fundamental law is followed by the mechanical wave? Answer: Laws of reflection.

Question 9. Which physical phenomenon is also based on reflection of sound waves? Answer: Phenomenon of echo.

Question 10. Which type of medium is necessary for the propagation of mechanical waves? Answer: A material medium.

Question 11. What should be the properties of the medium for the propagation of sound waves? Answer: The medium must possess three properties, viz. elasticity, inertial and minimum friction, and density of the medium.

Question 12. What is the physical cause that produces the sensation of hearing? Answer: Vibrations of the source.

Question 13. Give two applications in real-life where reflection of sound plays an important role? Answer: The ear trumpt or hearing aid, reflecting boards fixed inside the walls of large movie hall/auditorium.

Question 14. In which form longitudinal wave motion travels in a medium? Answer: It travels in the form of compression and rarefaction in the medium.

Question 15. ‘What are the changes involve in a medium during the propagation of longitudinal waves? Answer: Change in volume and density of the medium.

Question 16. Why the sound waves cannot travel through air in the form of transverse waves? Answer: Because crest and trough cannot be sustained in air.

NCERT Lab Manual Questions

Question 1. While performing this experiment, why do we prefer to use pipes of larger length but of smaller diameter? Answer: In this experiment, it is assumed that sound source is directional. Practically, due to the presence of unwanted sound in our surroundings, sound coming from source will not remain unidirectional. Therefore, it is advised to use the pipes of larger length but of smaller diameter.

Question 2. How the experiment of reflection of sound is different from the experiment on laws of reflection of light? Answer: For the reflection of sound wave, the surface may be polished or rough while the reflecting surface for light wave should be smooth and well polished.

Question 3. Which sheet will you choose as sound reflecting surface for this experiment; (a) A smooth wooden board or (b) A thermocol sheet? Why? Answer: A smooth wooden board will be chosen as sound reflecting surface because reflection from this surface will be more. Thermocol sheet acts as a good absorber of sound.

Question 4. Suppose the whole experimental set-up of this experiment is submerged in water. What changes do you expect in your observations? Answer: The speed of sound in water at 20 °C is 1482 ms-1 while in air it is 343 ms-1 at 20 °C. Therefore, when the whole experimental set-up is submerged in water, the reflected sound will be heard faster as compared to air.

Question 5. Why do we require a low amplitude sound source in this experiment? Answer: If we take the high amplitude sound source, then we may hear the sound from the source to our ear directly and not through the reflecting ray pipe. Therefore, it is required to have a low7 amplitude sound source in this experiment.

Question 6. What alterations can be made in the pipes to make the reflected sound more distinct and clear? Answer: In order to absorb all unwanted sound rays from our surroundings and to make the reflected sound more distinct and clear, the inner surfaces of two pipes should be painted black and kept rough. A rough paper is a good absorber of sound so when we use plastic pipes, a layer of newspapers may be inserted into these pipes.

Practical Based Questions

Multiple Choice Questions/VSA (1 Mark)

Question 2. In the experiment of verification of reflection of sound, the incident sound is directed along [CBSE 2010] (a) axis of tube (b) normal to the axis of tube (c) at an angle of 30° from the axis of the tube (d) at an angle of 45° from the axis of the tube.

Question 3. While verifying the laws of reflection of sound, out of following precautions which one should not be followed? [CBSE 2011] (a) The table top should be horizontal. (b) Length of pipes should be sufficiently long. (c) The reflecting surface should be smooth and hard. (d) Ear should not be placed close to the pipe.

Question 5. A student while verifying the laws of reflection of sound measured the angle between the incident sound wave and reflected sound wave as 130°. The angle of reflection is [CBSE 2012] (a) 130° (b) 65° (c) 90° (d) 60°

Question 6. The sound of a stopclock received in the ear while doing the experiment of ‘Reflection of sound’ should be [CBSE 2011][NCT 2009] (a) the direct sound from the clock. (b) the sound reflected from the ceiling of the laboratory. (c) the sound coming through the pipe after reflection from the reflecting surface. (d) both (a) and (b).

Question 7. A student performs the experiment of ‘reflection of sound’. He/she records following values of the angle of incidence and angle of reflection. [CBSE 2011]

  The set correctly recorded by him/her are (a) Set 1 and set 3 respectively. (b) Set 1 and set 5 respectively. (c) Set 2 and set 4 respectively. (d) Set 3 and set 5 respectively.

Question 8. In order to hear an echo of a sound wave, the minimum distance between the sound producing body and the reflecting surface should be (at normal temperature) (a) 20 m (b) 17.2 m (c) 21.6 m (d) 24.0 m

Question 9. When the sound wave propagates, which physical quantity changes in the medium? (a) Only density (b) Only pressure (c) Both density and pressure (d) Only frequency.

Question 11. If the reflecting surface and the source of sound both are in the plane of the table, the position of the ear of the observer should be (a) on the same plane (b) on the plane at an angle of 30° to the table. (c) on the plane at an angle of 90° below the table (d) perpendicularly above the source.

Question 12. Bats search out prey and fly in dark night by (a) emitting and detecting reflection of ultrasonic wave (b) emitting and detecting retraction of ultrasonic wave (c) emitting and detecting reflection of infrasonic wave (d) all of the above.

Question 13. Ramjeet, while verifying the laws of reflection of sound, measured the angle between the incident sound wave and reflected sound wave to be 130°. The angle of incidence is [NCT 2008] (a) Data insufficient (b) 65° (c) 130° (d) 25°

Question 16. Two students while performing experiment on verification of laws of reflection of sound are provided with the following choices:

• Using a narrow tube or wide tube
• Using a faint source of sound or strong source of sound.

The best results would be obtained by the student using the combination of: (a) narrow tube and faint source of sound (b) narrow tube and strong source of sound (c) wide tube and faint source of sound (d) wide tube and strong source of sound.

Short Answer Questions (2 Marks)

Question 1. In the experiment, to verify the laws of reflection of sound, the tube facing the clock makes an angle equal to 40° with the reflecting surface. What will be the position of the second tube with respect to the normal, at which the ear will get the best reflected sound? Answer: For perfect reflection, ∠i = ∠r Here, 40° + ∠i = 90° ⇒ ∠i = 90° – 40° = 50° = ∠r Hence, second tube should be placed at angle of 50° with the normal.

Question 2. Why is it important to have a smooth reflecting surface in the experiment, to verify the laws of reflection of sound? Answer: When sound wave is incident on any surface, some part of it is reflected and some part gets absorbed by that surface. For a smooth reflecting surface, the reflection will be more. Hence the sound that you hear through the pipe depends on the nature of the reflecting surface and thus, it is important to have a smooth reflecting surface.

Question 3. How can you show experimentally in this experiment that the reflected ray lies in the same plane of the incident ray? Answer: When the pipe, through which the sound is being heard, is lifted vertically to a small height, the sound from the low-amplitude source such as table-clock or mobile phone is either weakened or diminished completely. It shows that the reflected ray lies in the same plane of the incident ray.

Question 4. While performing the experiment, to verify the laws of reflection of sound, it is advisable to put the fan off. Why? Answer: In this experiment, it is required to hear very low- amplitude sound waves, so peaceful atmosphere is the necessary condition for performing the experiment. To hear such sounds clearly, it is further advised to put the fan off.

Question 5. Why are curved sound boards and sound absorbent materials used in halls and auditoriums? On which phenomenon of sound it is based? Answer: Curved sound boards spread sound uniformly to all places of the hall and auditorium. Draperies and other sound absorbing materials reduce the persistence of sound in hall so that original sound is clearly heard. It is based on the multiple reflections of sound waves from the surface.

Science Practical Skills Science Labs Math Lab Manual Math Labs with Activity Math Labs

• Sound Waves
• Sound Reflection

Reflection of Sound and Its Application

The concept of reflection of sound is familiar to everyone. Let’s understand this through a small activity. If we take two tubes and position them against a wall, as shown in the figure below, upon placing a speaker or any other source of sound near one end of the tube, we receive the sound at the end of the other tube. This activity proves that the surface of the wall reflects the sound wave. In this section, we shall learn more about the reflection of sound and its application in day-to-day life.

Sound: Definition

Sound is defined as oscillations or auditory sensations evoked by oscillations in particle displacement or velocity, propagated in a medium with internal force. Sound propagates as a mechanical wave, through a medium such as air or water.

Reflection of Sound

Just like the reflection of light, the reflection of sound is similar as it follows the laws of reflections, where the angle of reflection is equal to the angle of incidence and the reflected sound, the incident sound, and the normal sound belong in the same plane. Sound bounces off the surface of the medium which can be a solid or a liquid. In order to make the reflection of sound to occur, the surface can be of large size and can be either rough or polished.

Laws of Reflection of Sound

• The angle of reflection is always equal to the angle of incidence .
• The reflected sound, the incident sound, and the normal sound belong in the same plane.

Read More: Angle of Incidence

Applications of Reflection of Sound

The sound heard after reflections from a rigid surface such as a cliff or a wall is called an echo creating a persistence of sound even after the source of sound has stopped vibrating. The echo is used by bats and dolphins to detect obstacles or to navigate. The same principle is used in SONAR (Sound Navigation And Ranging technique), used in oceanographic studies. SONAR is used for the detection and location of unseen underwater objects, such as submerged submarines, sunken ships, and icebergs. In SONAR, ultrasonic waves are sent in all directions from the ship and the received signal is analysed.

Hearing Aid:

A hearing aid is a device used by people with difficulty in hearing. Here, the sound waves are received by the hearing aid and are reflected in a narrower area leading to the ear.

Megaphones are horn-shaped tubes that prevent the spreading out of sound waves by successive reflections, thus confining them to the air in the tube.

Sound Board:

Sound boards are curved surfaces that are placed in such a way that the sound source is at the focus. The sound waves are made to reflect equally throughout the hall or an auditorium thus enhancing their quality.

Watch the video and learn more about the reflection of sound waves

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Frequently Asked Questions – FAQs

Define sound., what are the laws of reflection of sound.

• The angle of reflection is always equal to the angle of incidence.

What is an echo?

Define the intensity of sound., why is the speed of sound maximum in solids, the below video helps to completely revise the chapter sound class 9.

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• REFLECTION OF SOUND
• Active page

Sound of Class 9

When sound waves strike a surface, hey return back into the same medium. This phenomenon is called reflection.

The reflection of sound waves is similar to that of light rays. The only difference is that sound waves being larger in length. require bigger surfaces for reflection

LAWS OF REFLECTION:

• Angle of incidence is equal to the angle of reflection.
• The incident wave, the reflected wave and the normal, all lie in the same plane.

VERIFICATION OF LAW OF REFLECTION:

APPLICATIONS OF REFLECTION OF SOUND:

Mega phone or speaking tube:

When we have to call someone at a far off distance (say 100m), we cup our hands and call the persons with maximum sound we can produce. The hands percent the sound energy from spreading in all directions. In the same way, the people use horn shaped metal tubes, commonly called megaphones. The loud speakers have horn shaped openings. In all these devises, the sound energy is prevented from spreading out by successive reflections from the horn shaped tubes.

Working: The metal case C containing the diaphragm is gently pressed against the part of the body to be examined. The vibrations of this part are communicated to the diaphragm Dwhich starts vibrating. As shown in figure, these vibrations suffer multiple reflections in the tubes R, T, T1 and T2 and ultimately reach the earphones. The original sound produced by the part of the human body is exactly reproduced in the earphones and a preliminary diagnosis of the ailment is made.

• Ear trumpet: It is a sort of machine used by persons who are hard of hearing. The sound energy received by the wide end of the trumpet is concentrated into a much smaller area at the narrow end by multiple reflections. This makes the otherwise inaudible sound audible to the user.
• Hearing aid: An ear trumpet is a mechanical device helpful only to a person with mild hearing loss. A hearing aid is an electronic device which is battery operated and is used by people with severe hearing loss. A hearing aid is fitted with a microphone which converts sound waves into electrical signals. An electronic amplifier amplifies these signals which are then fed to a speaker in the hearing aid. The speaker converts the amplified electrical signals into sound which is sent to the ear for clear hearing.
• So und board : The sound waves obey the laws of reflection on the place as well as curbed reflecting surfaces. In order to spread sound evenly in big halls or auditoriums, the speaker (S) is fixed at the principle focus of the concave reflector. This concave reflector is commonly calledsounding board. The sound waves striking the sound board get reflected parallel to the principal axis.
• SOUND NEEDS A MATERIAL MEDIUM FOR ITS PROPAGATION
• Introduction sound
• THE HUMAN EAR
• NATURE OF SOUND
• PRODUCTION OF SOUND WAVES
• PROPAGATION OF SOUND
• CHARACTERISTICS OF SOUND
• RANGE OF HEARING
• SPEED OF SOUND IN DIFFERENT MEDIUM
• EFFECT OF TEMPERATURE ON THE SPEED OF SOUND
• RELATION BETWEEN SPEED OF SOUND, TIME OF HERING ECHO-AND DISTANCE OF REFLECTING BODY
• AUDIBLE, INFRASONIC AND ULTRASONIC WAVES
• REASON FOR USING ULTRASONIC WAVES IN SONAR
• Solved questions
• Exercise 4 (Fill in the blanks)
• Exercise 5 (Subjective)

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