class 08 Sound and Its Reflection: Multiple Choice Questions

Chapter Sound and Reflection of sound        Objective:  Multiple choice Questions

1. A sound wave travels from east to west, in which direction do the particles of air move?

(A) East – west                           (B) North - south

(C) Up and down                         (D) None of these

2. In which medium sound travels faster ?

(A) Solid                                   (B) Liquid

(C) Gas                                      (D) None of these

3. What is the name of short duration wave?

(A) Pulse                                    (B) Frequency

(C) Time period                            (D) Velocity

4. What is the velocity of sound in water at room temperature?

(A) 1500 m/s                             (B) 340 m/s

(C) 1500 km/s                         (D) 330 km/s

5. The unit of quantity on which pitch of the sound depends is :

(A) Hertz                                    (B) metre

(C) metre/second                       (D) second

6. The unit of quantity on which loudness of found depends is :

(A) metre                                   (B) Hertz

(C) metre/second                      (D) Decibel

7. Nature of sound wave is :

(A) transverse                          (B) longitudinal

(C) electromagnetic                   (D) seismic

8. Pitch of high frequency sound is :

(A) high                                     (B) low

(C) zero                                     (D) infinite

9. Voice of a friend is recognized by its :

(A) Pitch                                     (B) quality

(C) Intensity                               (D) velocity

10. S I unit of Intensity of Sound waves is :

(A) watt/m^2                              (B) j/s

(C) w/m                                      (D) kwh

Ans: . 1-A                  2-A                     3-A              4-A                 5-A           6-A      7-B              8-A                 9-B         10-A

Objective:  Fill in the blanks

1. Pitch is the sensation  of the ---------- of an emitted sound.

2. A high pitch sound is called a ------ sound

3. A low pitch sound is called a -----------  sound.

4. Loudness of sound wave is ditectly proportional to -------- amplitude

5. The sound energy transferred per unit area per unit time is called -------- of sound.

6. When a body moves with a speed which is greater than the speed of sound in air, it is said to be traveling at --------------

7. When wound waves traveling in air enter into the medium of water, ------- remains unchanged

8. Sound travels faster as the  ------------ of the medium increases by 0.61 m/s with every 1 deg C    9. -----is an apparatus which is used to find the depth of a sea or to locate the under water things.

10. A sound wave of single frequency is called ---------

Ans: 1. Frequency  6. supersonic speed 2. shrill 7. Frequency 3. hoarse 8. temperature 4. Square 9. Sonar 5. intensity 10.Tone

CLASS VIII physics Chapter Sound Solve CBSE Exam Assignments

Q.1 How does a sound making object differ from one that is silent?

Answer: Sound making object can vibrate easily.                      

Q.2 How does sound from a sound producing body travel through air to reach our ears?

Answer: Sound from a sound producing body travel through air to reach our ears by making regular compression and rarefaction.
Q.3  Why are the voices of men, Women and children different?

Answer: The voices of men, women and children differ from each other due to the following factors:

1) The pitch is one of the most essential factors to determine the voice of the individual. For example, men have lower-pitched voices while women have higher-pitched voices.

2) Second factor which brings in the difference in the voices is the length and the thickness of vocal cords.

Q.4  Why a sound cannot be heard on the moon?

Answer: A sound cannot be heard on the moon due to absence of medium air

Q.5  How do astronauts talk to one another on the surface of moon and Why?
Answer:  Astronauts communicate with the help of radio waves on moon because these waves do not need a medium to travel

Q.6  If you want to hear a train approaching from far away, why is it more convenient to put the ear to the track?
Answer: This is because sound can travel through railway track (solid ) faster than through air.

Q.7  State one observation from everyday life which shows that sound travels much more slowly than light?
Answer: We hear thunder after lightining.

Q.8  What is the scientific name for the following? The number of vibrations made per second.
Answer: Frequency

Q.9   Why do we not hear the screams of a bat?

Ans: This is because the screams are ultra sonic(above 20,000 hertz) which human ear cannot hear.
Q.10  Which of the following frequency of sound can be heard by a dog but not by a man?                                                                     (a) 50,000 hertz (b)   15,000 hertz
Answer:  A sound of frequency 50,000 hertz can be heard by a dog but not by a man

Q.11 Explain how, noise pollution {or excessive loud noise} is harmful to human beings.
Answer: Noise pollution can lead to a number of health-related problems. Some of them are as follows:

(i) Hearing loss  (ii) inability to sleep         (iii) Hypertension (iv) Severe headache (v) Stress

Q.12  State the various measures which can be taken to control {or reduce} noise pollution in our surroundings.
Answer: Noise pollution can be reduced by using silencers in vehicles, industrial machines, and home appliances reducing use of vehicle horns, running TV, radio and music systems at low volumes. Planting of trees along roads and buildings also help to reduce noise pollution.

Q.13 Give two causes of noise pollution from the homes.
Answer: . In the home noise pollution is caused by television radio and  music systems at high volume, some kitchen appliances, desert coolers, air conditioners etc.

Q.14   Sound of different pitch can be produced using a flute. Explain, how?  

Answer: If we blow a flute, the air column vibrates and produces sound. Flute contains small air columns, when air is bowed through the mouth piece the air columns start vibrating which produces sound.

Q.15.How does Sound produced by humans?

Answer:     In humans sound is produced by the vioce box or larynx. It is the upper part of the wind pipe. Two vocal cords are stretched across the voice box leaving a narrow slit. When the lungs force air through the slit, it vibrates and produces sound.

Q. 16. How Jal Tarang produces sound?

Answer: In Jal-tarang musical instrument the cup containing minimum water produces the sound of lowest frequency or lowest pitch. As the amount of water in the cup goes on increasing, the frequency (or the pitch) of the sound produced also goes on increasing.

Q. 17. If 125 oscillations are produced in 5 seconds, what is the frequency in hertz?

Answer: in 5 seconds 125 oscillations are produced

So, in 51 seconds 125/5 = 25 oscillations are produced

Hence, the frequency = 25Hz

Q. 18. What is the frequency of a vibrating body whose time-period is 0.05 second?              

Answer: f = 1/t = 1/0.05 = 100/5 = 20HZ

Q. 18. State true or false

(i) Sound can be produced by beating an object irrespective of whether there are vibrations or not.

(ii)The sound of a tabla normally has a lower pitch than the sound of a violin.

(ii)A short flute will produce sound of lower pitch than a long flute.

Answer: (i) –False [Sound is produced from a vibrating object.]

(ii) -True [The sound of a tabla normally has a lower pitch than the sound of a violin.]

(iii) –True[A short flute will produce sound of lower pitch than a long flute.]

Q.19. Give reasons Why Trees planted along the roads reduce noise?

Answer: Trees are planted along the roads and around buildings so that it could cut off sound vibrations produced from vehicles speakers etc. by absorbing them, hence leading in prevention of Noise pollution.

Q.20. what are transverse and longitudinal waves?

Answer: Longitudinal waves: A wave in which the particles of the medium vibrate back and forth in the same direction in which the wave is moving is called longitudinal wave. Example: sound waves.

Transverse waves: A wave in which the particles of the medium vibrate at right angles to the direction, in which the wave is moving, is called transverse wave. Example: Light waves.

Assignments for practice 

1. How sound is produced?

2. What do you understand by a ‘wave’?

3. Write three differences between sound and light waves.

4. What do you understand by “sound energy cannot be produced”?

5. What is the name of the wave that can travel through vacuum?

6. Explain by some experiment that sound waves require medium for their propagation.

7. How sound waves travel through some medium?

8. Why sound waves do not propagate through vacuum?

9. What are the transverse waves? Give two examples.

10. What are longitudinal waves? Give two examples.

11. Give two points of difference between longitudinal and transverse waves.

12. How will you prove that the sound waves exhibit longitudinal behaviour?

13. What are rarefaction and compression in case of sound waves?

14. Distinguish between crests and troughs.

15. Write the SI unit of velocity of a wave.

16. What are the factors that describe the sound wave and define them?

17 Why is a thundering sound heard later than lightening?

18. Sound travels with different speeds in different media. Comment.

19. How far is a compression and its nearest rarefaction in a longitudinal wave?

20. Define sound ranging.

21. What is the frequency range of sound for human beings?

22. What are the ultrasonic and supersonic waves?

23. What type of waves are produced by animals like bats and dolphins?

24. Explain two applications of ultra sound waves?

25. Explain how ultrasound waves are used to detect a flaw in an object?

26. Which sound wave is used in ECG (echocardiography)?

27. Give the full form of SONAR.

28. Name the technique used to measure the depth of a sea.

29. How will you determine the depth of a sea using SONAR?

30. How do the bats fly in dark?

31. How RADAR is different from SONAR?

32. Explain the function of ear by explaining its each part.

NCERT 9th Physics Question Bank For - Sound

1.What are the uses of SONAR technique?

2. What does ‘SONAR’ stand for?

3.Which part of the ear turns pressure variations into electrical signals?

4.What is intensity of sound?

5. Why sound wave is called longitudinal wave?

6. What is a sound?

7. Why sound waves are called mechanical waves?

8. What is a crest and a trough in a wave?

9.Can sound wave travel through vacuum?

10. What is amplitude of a wave?

11. What is characterized by the amplitude of the wave?

12. What is characterized by the frequency of the sound wave?

13.What is reverberation?

14.What is the audible range of the average human ear?

15. In sound propagation, do

16. Does speed of sound in a

17. What should be the minimum distance between a sound source and reflector for a distinct echo?

18. What is a wave?

19. Explain why the ceilings of concert halls and conference halls made curved?

20. What is law of reflection in sound?

21. Priya clapped her hand near a cliff and heard the echo after 5 second. If the speed of sound be

330 m/sec, then find the distance of the cliff from priya?

22. What are ‘infrasonic’ and ‘ultrasonic’?

23. Calculate the time in which a tuning fork of frequency 234 Hz completes 26 vibrations.

24. We hear thunder sound a few seconds after the flash is seen even though they occur simultaneously. Why?

25. A sound wave has a frequency of 1500Hz and wavelength 25cm. How long will it take to travel 3

km?

26. Why and how is reverberation removed in an auditorium or a big hall?

27. State Laws of Reflection of Sound

28. Harry standing 440 m away from a wall fired a gun and heard its echo 2 s later. How is an echo

formed? Calculate the velocity of sound in air.

29. Explain how ultrasounds help to detect cracks and flaws in metal blocks.

30. Define time period of sound wave. What is its SI unit? How is it related with frequency?

31. Explain how compressions and rarefactions are produced in air near a source of sound.

32. How does sound reaches our ears?

33. What will happen to the loudness of a sound wave if its amplitude is doubled? Name a unit of

sound. Is loudness affected by change in frequency?

34. How do sound waves propagate?

35. Are the particles of the medium dragged along with the wave as sound wave propagates through

the medium? In which medium—solid, liquid or gas, does the sound wave travel fastest? 

36. State any two characteristics of sound wave?why it is called mechanical wave? Find the distance

traveled by a sound wave of frequency 20 K Hz, wavelength 1.7 cm in 10 s.

37. .What are differences between music and noise?

38. How bat is able to fly in night?

39 .Discuss effect of temperature and humidity on speed of sound.

40.Why lightining appears before than thundering in rainy season?

IX Physics key concept Ch. Sound

1. Sound is a wave that is created by vibrating objects and propagated through a medium from one location to another.

2. A disturbance that travels through a medium, transporting energy from one location to another location is called wave. The medium is simply the material through which the disturbance is moving; it can be thought of as a series of interacting particles.

3. In our body Vocal cord is vibrating body that produce sound wave.

4. The sound wave is transported from one location to another by means of particle-to-particle interaction like air particles in air.

5. Air particles interact continuously throughout the entire medium that causes disturbance to its nearest neighbours till sound reach to listener.

6. A sound wave is a disturbance that is travel through a medium via the mechanism of particle-to-particle interaction. Hence sound wave is characterized as a mechanical wave.

7. Longitudinal waves are waves in which the particles of the medium propagate is in a direction that is parallel to the direction of energy transport.

8. Sound waves in air (and any fluid medium) are longitudinal waves because particles of the medium through which the sound is transported vibrate parallel to the direction that the sound wave move.

9. The back and forth vibration of the string causes individual air molecules These back and forth vibrations are imparted to adjacent neighbours by particle-to-particle interaction. Other surrounding particles begin to move rightward and leftward, thus sending a wave to the right.

10. Air molecules are moving in a direction that is parallel to the direction that the wave moves, the sound wave is referred to as a longitudinal wave

11. In longitudinal wave, the compressions are regions of high air pressure while the rarefactions are regions of low air pressure

12. The wavelength is commonly measured as the distance from one compression to the next adjacent compression or the distance from one rarefaction to the next adjacent rarefaction.

13. A sound wave consists of a repeating pattern of high-pressure and low-pressure regions moving through a medium, it is sometimes called pressure wave.

14. The particles of the medium through which the sound moves when vibrating a back and forth motion is called its frequency.

15. If a particle of air vibrate 100 times in 2 seconds, then the frequency of the wave would be 50 vibrations per second. Unit for frequency is the Hertz (abbreviated Hz).

16. 1 Hertz = 1 vibration/second

17. Human ear is capable of detecting sound waves with a wide range of frequencies, ranging between approximately 20 Hz to 20 000 Hz

18. Any sound with a frequency below the audible range of hearing (i.e., less than 20 Hz) is known as an infrasound

19. Any sound with a frequency above the audible range of hearing (i.e., more than 20 000 Hz) is known as an ultrasound.

20. The sensation of a frequency is known as the pitch of a sound.

21. The time taken for one oscillation is called time period.

22. The amount of energy that is transported through a given area of the medium per unit of time is known as the intensity of the sound wave. Intensity is the energy/time/area or power/area.

23. Units for the intensity of a sound wave are Watts/meter2.

24. The speed of a sound wave in air at a temperature of 20 degrees Celsius= 343 m/s

25. The maximum displacement of an oscillating body from its central position is called its amplitude

26. The loudness of sound depends upon the amplitude of vibration. If the amplitude is less the sound is feeble. If the amplitude is more the sound is loud. The unit of loudness is called decibel (dB).

27. The pitch of sound depends upon the frequency of vibration. If the frequency is less the sound has low pitch. Eg :- sound of a drum, sound of an adult etc. If the frequency is more the sound has a high pitch. Eg :- sound of a whistle, sound of a baby etc.

28. The mathematical relationship between speed, frequency and wavelength is Speed = Wavelength x Frequency

29. The Human Ear consists of three basic parts - the outer ear, the middle ear, and the inner ear.

30. The outer ear consists of an earflap and an approximately 2-cm long ear canal through sound waves reaches the eardrum

31. The middle ear is an air-filled cavity that consists of an eardrum and three tiny, interconnected bones - the hammer, anvil, and stirrup.

33. The eardrum amplify sounds with frequencies of approximately 3000 Hz

34. The movements of the eardrum will set the hammer, anvil, and stirrup into motion at the same frequency of the sound wave.

35. The inner ear consists of a cochlea, the semicircular canals, and the auditory nerve.

36. Cochlea converts sound wave frequency into electrical impulses.

37. The auditory nerve transfer electrical impulses towards the brain.

38. The brain is capable of interpreting the qualities of the sound upon reception of these electric nerve impulses.

39. Noise :- Unpleasant sounds are called noise. It is produced by irregular vibrations. Eg :- If all the students in a classroom speak together, a noise is produced. Sounds produced by horns of busses and trucks.

40. Musical sound :- Sound which is pleasing to the ears is called musical sound. It is produced by regular vibrations. Eg :- Sounds produced by musical instruments. Sound of a person singing a song.

IX Physics Ch. Sound as a wave part-1

Sound is a wave caused by the movement of particles that travels through air or water similar to the ripples on a pond or the ocean waves you might see on a beach.

A wave can be described as a disturbance that travels through a medium from one location to another location or, The repeating and periodic disturbance which moves through a medium from one location to another is called a wave.

There are two types of waves: Mechanical waves and electromagnetic waves

Electromagnetic waves are waves traveling through a vacuum and  do not require a medium in order to transport their energy(propagation) e.g. Light

Mechanical waves are waves which require a medium for propagation or to transport their energy from one point to another. It is of two types.

Longitudinal wave :  A  mechanical waves in which the particles and the energy move in the same direction  parallel to the direction in which the wave is travelling.

 A sound wave traveling through air is example of longitudinal waves because particles of the medium through which the sound is transported vibrate parallel to the direction which the sound wave moves.

Compressions are the regions where particles are crowded together. The peak represents the region of maximum compression. Thus, compressions are regions where density as well as pressure is high. 

Rarefactions are the regions of low pressure where particles are spread apart.

The distance between two consecutive compressions (C) or two consecutive rarefactions (R) is called the wavelength. 

The wavelength is usually represented by λ (Greek letter lambda). Its SI unit is metre (m).

Transverse wave: A wave in which particles of the medium move in a direction perpendicular to the direction which the wave is travelling. The particles of medium vibrate up-and-down and the energy moves left-and-right. e.g. Water waves on the ocean surface.

A peak is called the crest and a valley is called the trough of a wave.

Propagation of Sound

The matter or substance through which sound is transmitted is called a medium. It can be solid, liquid or gas.

How does the sound produced by a vibrating object in a medium reach your ear?

When an object vibrates, it sets the particles of the medium to vibrate. It then exerts a force on the adjacent particle and displace from its position of rest. This process continues in the medium till the sound reaches your ear.

Why sound waves are called mechanical waves?

In the propagation of sound the particles of the medium do not move forward themselves, but the disturbance is carried forward through medium. Hence,  sound is a form of a wave. As it needs material medium for propagation it is a mechanical wave.

Air is the most common medium through which sound travels. When a vibrating object moves forward, it pushes and compresses the air in front of it creating a region of high pressure. This region is called a compression

  

This compression  starts to move away from the vibrating object. When the vibrating object moves backwards, it creates a region of low pressure called rarefaction (R)

Hence , a  series of compressions and rarefactions is created in the air make the sound wave propagates through the medium.

Explain how sound is produced by school bell.

When school bell is hit by a hammer, the bell continues to move forward and backward, that creates a series of compressions and rarefactions. This produces the sound of a bell.

Suppose you and your friend are on the moon. Will you be able to hear any sound produced by your friend? 

Sound needs a medium to propagate. Since there is no material medium on the moon due to absence of atmosphere, you cannot hear any sound on the moon. 

In which of the three media, air, water or iron, does sound travel the fastest at a particular temperature? 

The speed of sound depends on the nature of the medium. Sound travels the fastest in solids. Its speed decreases in liquids and it is the slowest in gases.  Therefore, for a given temperature, sound travels fastest in iron.

How a sound wave propagates?

When sound wave propagates the particles do not move from one place to another but they simply oscillate back and forth about their position of rest. The individual particles of the medium move in a direction parallel to the direction of propagation of the disturbance. A sound wave traveling through air is example of longitudinal waves

We can describe a sound wave by its properties

(a) Frequency (b) amplitude and   (c) speed.

The number of such oscillations per unit time is the frequency of the sound wave. If we can count the number of the compressions or rarefactions that cross us per unit time, we will get the frequency of the sound wave. It is usually represented by n .Its SI unit is hertz (symbol, Hz).

The time taken for one oscillation is called time period. It is represented by the symbol  T. Its SI unit is second (s).

Frequency and time period are related as follows:  n=1/T

Pitch:  How the brain interprets the frequency of an emitted sound is called the pitch. The faster the vibration of the source, the higher is the frequency and the higher is the pitch.

The amplitude of the sound : The magnitude of the maximum disturbance in the medium on either side of the mean value is called the amplitude of the wave. It is usually represented by the letter A. The amplitude of the sound wave depends upon the force with which an object is made to vibrate

The quality or timber of sound is that characteristic which enables us to distinguish one sound from another having the same pitch and loudness. The sound which is more pleasant is said to be of a rich quality.

Notes and Tone: A sound of single frequency is called a tone.  The sound which is produced due to a mixture of several frequencies is called a note

Noise and Music :  The sound which is  pleasant to listen is called music .  The sound which is unpleasant to listen is called noise .

The speed of sound:  The distance (a compression or a rarefaction) travels per unit time is called the speed of sound. 

speed, v = distance / time = wave length/ time =  l/ T = l x (1/t)

or,   v = nl ( as n=1/T)

Speed = wavelength × frequency

IX-VIII-Physics Refraction of Sound Explanation

Sound plays an important part in our daily lives. It helps us to communicate with each other. We hear a wide variety of sounds in our surroundings.
Sound is produced by a vibrating body. Vibration is the to and fro or back and forth motion of an object. Eg :- If you strike a school bell, it vibrates and produces sound. If you pluck a stretched rubber band, it vibrates and produces sound. If you beat a drum, its stretched membrane vibrates and produces sound. If you blow a bugle, the air column vibrates and produces sound.

Musical instruments and their vibrating parts :-

Sl.No.	Musical instrument	Vibrating part producing sound
1	Veena	Stretched string
2	Sitar	Stretched string
3	Violin	Stretched string
4	Tabala	Stretched membrane
5	Mridangam	Stretched membrane
6	Drum	Stretched membrane
7	Shehnai	Air column
8	Flute	Air column
9	Mouth organ	Air column

 Some musical instruments produce sound when they are beaten or struck. Eg:- bell, ghatam, manjira, jaltarang etc 

How Sound is produced by humans: 

In humans sound is produced by the voice box or larynx. It is the upper part of the wind pipe. Two vocal cords are stretched across the voice box leaving a narrow slit. When the lungs force air through the slit, it vibrates and produce sound.

Sound travels through solids, liquids and gases. Sound does not travel in vacuum. Eg :- Sound travels through the solid thread of a can telephone.   A whale listens to the reflected sound (echo) in water to locate   its prey. We are able to listen to sounds because sound travels in air.

Sound enters the ear through the ear canal. It makes the eardrum to vibrate. The ear drum sends the vibrations to the inner ear. From there the signals go to the brain and then we hear the sound

Vibration is the to and fro motion of an object. It is also called oscillatory motion. 

i) The maximum displacement of an oscillating body from its central position is called its amplitude. (OB or OA)
ii) The motion of the pendulum from one extreme position to the other extreme position and back is called an oscillation. (A to B and back to A)

iii) The time taken for one oscillation is called time period.
iv) The number of oscillations per second is called frequency. The unit of frequency is hertz (Hz).

The loudness of sound depends upon the amplitude of vibration. If the amplitude is less the sound is feeble. If the amplitude is more the sound is loud. The unit of loudness is called decibel (dB).

The pitch of sound depends upon the frequency of vibration. If the frequency is less the sound has low pitch. Eg :- sound of a drum, sound of an adult etc. If the frequency is more the sound has a high pitch. Eg :- sound of a whistle, sound of a baby etc.

Audible sound is sound which we can hear. It has frequencies between 20 Hz and 20000 Hz. (Between 20 and 20000 vibrations per second).

Inaudible sound is sound which we cannot hear. It has frequencies less than 20Hz and more than 20000 Hz. (Less than 20 vibrations per second and more than 20000 vibrations per second)

Sound whose frequencies are more than 20000 Hz is called ultrasonic sound. Some animals like dogs can hear ultrasonic sound. Bats produce ultrasonic sound.

Noise - Unpleasant sounds are called noise. It is produced by irregular vibrations. Eg :- If all the students in a classroom speak together, a noise is produced. Sounds produced by horns of busses and trucks.
Musical sound :- Sound which is pleasing to the ears is called musical sound. It is produced by regular vibrations. Eg :- Sounds produced by musical instruments. Sound of a person singing a song.

Noise pollution  The presence of excessive or unwanted sound in the environment is called noise pollution. 

a) Causes of noise pollution :- Noise pollution is caused by sounds of vehicles, explosions including bursting of crackers, machines, loudspeakers etc. In the home noise pollution is caused by television radio and music systems at high volume, some kitchen appliances, desert coolers, air conditioners etc.
b) Harmful effects of noise pollution :- Noise pollution causes several health related problems like lack of sleep, hypertension, high blood pressure, anxiety etc. A person exposed to loud sound continuously may get temporary or permanent impairment of hearing.
c) Measures to limit noise pollution :- Noise pollution can be reduced by using silencers in vehicles, industrial machines, and home appliances reducing use of vehicle horns, running TV, radio and music systems at low volumes. Planting of trees along roads and buildings also help to reduce noise pollution.

Class 8th science maths NCERT solutions and sample papers

8th Chapter Sound (2)
8th Chemical effects of electric current (2)
8th Force of Friction (1)
8th Light Reflection and Eyes (2)
8th Some Natural Phenomena (2)
8th THE Universe (3)

Mathematics

Physics class 9th Numerical for chapter sound

1. A person observe the smoke from a gun 1.4 sec before he hear the bang. If the gun is 476m away from the person,find the speed of sound?

2. A person standing near the cliff fires the gun and heared the echo after 1.5 sec . If the speed of sound in air is 340m/sec , how far is person from the cliff?

3. A sound wave of frequency 5000 Hz travel in air with speed of 350m/sec. Calculate the wave length.

4. If u hear thunder 7 sec after u see yhe lightining , how far u from the lighting occurred?

5. A bat emits ultrasonic wave of frequency 30 Khz..If its speed is 350m/s and bats hear its echo after 0.6 sec after emitting the , find how far is bat from obstacle and wave length of wave?

6. Meera is standing between two hills.She shouted loudly and hears first echo after 0.5 sec and second echo after 1 sec. what is distance between two hills? 7. If 2000 ripples produced in 5 sec in a pond find time period and frequency of ripples formation.

8. A man standing in a valley between two parallel mountains fires a gun and hears echo at an interval of 2 s and 3.5s. what is a) the distance between two mountains b) the location of the man with respect to the mountain.

9. Calculate the wavelength of a sound whose frequency is 220 Hz and speed is 440 in a given medium.

10. A body is vibrating 6000 times is 1 minute. If the velocity of sound in air is 360 m/s, find
(i) Frequency in Hz   (ii) wavelength of sound.

11. . A stone is dropped from a 500 m tall building into a pond. When is sound splash heard? Given g=10 m/s2 , speed of sound = 340 m/s.

12. An echo is heard in 3 sec after the emission of sound. If speed of sound in air is 342 m/s, what is the distance of the reflecting surface from the source?

Solution : Class 09 Sound solved Numerical Test Paper-1
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Class 09 Sound solved CBSE Test Paper-2
Class 09 Sound solved CBSE Test Paper-3
Class 09 Sound solved CBSE Test Paper-4

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Physics class 9th Numerical for chapter sound
9th Question Bank chapter -Sound
9th Sound Test Paper