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# Lakhmir Singh solutions for Science for Class 9 Physics chapter 5 - Sound [Latest edition]

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## Chapter 5: Sound

#### Lakhmir Singh solutions for Science for Class 9 Physics Chapter 5 SoundExercise Very Short Answers, Short Answers, Long Answers, MCQ, Hots Questions [Pages 185 - 188]

Very Short Answers | Q 1 | Page 185

Can sound travel through (a) iron, and (b) water?

Very Short Answers | Q 2 | Page 185

Can sound travel through vacuum?

Very Short Answers | Q 3 | Page 185

Name the type of waves which are used by astronauts to communicate with one another on moon (or in outer space).

Very Short Answers | Q 4 | Page 185

Name one solid, on liquid and one gas through which sound can travel.

Very Short Answers | Q 5 | Page 185

Which of the following cannot transmit sound? Water, Vacuum, Aluminium, Oxygen gas

Very Short Answers | Q 6 | Page 185

Name the physical qantity whose SI unit is 'hertz'.

Very Short Answers | Q 7 | Page 185

What is the SI unit of frequency?

Very Short Answers | Q 8 | Page 185

What type of wave is represented :
(a) by density-distance graph?
(b) by displacement-distance graph?

Very Short Answers | Q 9 | Page 185

Is the speed of sound more in water or in steel?

Very Short Answers | Q 10 | Page 185

In which medium sound travels faster : air or iron?

Very Short Answers | Q 11 | Page 185

In which medium sound travels fastest : air, water or steel?

Very Short Answers | Q 12 | Page 185

Out of solids, liquids and gases :
(a) in which medium sound travels slowest?
(b) in which medium sound travels fastest?

Very Short Answers | Q 13 | Page 185

Which of the following is the speed of sound in copper and which in aluminium?
(a) 5100 m/s
(b) 1500 m/s
(c) 3750 m/s

Very Short Answers | Q 14 | Page 185

If you want to hear a train approaching from far away, why is it more convenient to put the ear to the track?

Very Short Answers | Q 15 | Page 185

What is the speed of sound :
(a) in air?
(b) in water?
(c) in iron?

Very Short Answers | Q 16 | Page 185

What name is given to those aircrafts which fly at speeds greater than the speed of sound?

Very Short Answers | Q 17 | Page 185

A jet aircraft flies at a speed of 410 m/s. What is this speed known as?

Very Short Answers | Q 18 | Page 185

What is meant by supersonic speed?

Very Short Answers | Q 19 | Page 185

State one observation from everyday life which shows that sound travels much more slow than light.

Very Short Answers | Q 20 | Page 185

Name the two types of waves which can be generates in a long flexible spring (or slinky).

Very Short Answers | Q 21 | Page 185

A stone is dropped on the surface of water in a pond. Name the type of waves produced.

Very Short Answers | Q 22 | Page 185

Name the type of waves produced when a tuning fork is struck in air.

Very Short Answers | Q 23 | Page 185

What is the general name of the waves consisting of :
(a) compressions and rarefactions?
(b) crests and troughs?

Very Short Answers | Q 24 | Page 185

State the general name of the waves in which the particles of the medium vibrate :
(i) in the same direction as wave.
(ii) at right angles to the direction of wave.

Very Short Answers | Q 25 | Page 185

What type of waves are illustrated by the movement of a rope whose one end is fixed to a pole and the other end is moved up and down?

Very Short Answers | Q 26 | Page 185

What should an object do to produce sound?

Very Short Answers | Q 27 | Page 185

What is the name of the strings which vibrate in our voice box when we talk?

Very Short Answers | Q 28 | Page 185

Name the device which is used to produce sound in laboratory experiments?

Very Short Answers | Q 29 | Page 185

What is the nature of sound waves in air?

Very Short Answers | Q 30 | Page 185

What conclusion can be obtained from the observation that when the prongs of a sound making tuning fork touch the surface of water in a beaker, the water gets splashed?

Very Short Answers | Q 31 | Page 186

State whether the following statement is true or false :
Sound produced by a vibrating body travels to our ears by the actual movement of air.

Very Short Answers | Q 32 | Page 185

Which of the following travels slowest in air and which one fastest? Supersonic aircraft, Light, Sound

Very Short Answers | Q 33 | Page 185

Which term is used to denote a speed greater than the speed of sound?

Very Short Answers | Q 34 | Page 186

In which medium sound travels faster : air or hydrogen?

Very Short Answers | Q 35 | Page 186

A tuning fork has a number 256 marked on it. What does this number signify?

Very Short Answers | Q 36 | Page 185

What is the time-period of a tuning fork whose frequency is 200 Hz?

Very Short Answers | Q 37 | Page 186

Calculate the frequency of a wave whose time-period is 0.02 s.

Very Short Answers | Q 38 | Page 186

What will be the change in the wavelength of a sound wave in air if its frequency is doubled?

Very Short Answers | Q 39 | Page 186

If 20 waves are produced per second, What is the frequency is hertz?

Very Short Answers | Q 40.1 | Page 186

Fill in the blank with suitable word .
Sound waves are caused by ...................

Very Short Answers | Q 40.2 | Page 186

Fill in the blanks with suitable words.
A sound wave consists of places of higher pressure called ................. and places of................pressure called.................

Very Short Answers | Q 40.3 | Page 186

Fill in the blanks with suitable words .

Wave speed in metres per second equals frequency in ............ multiplied by ..................... in ..................

Very Short Answers | Q 40.4 | Page 186

Fill in the blank with suitable word.
Sound cannot travel through ____________.

Very Short Answers | Q 40.5 | Page 186

Fill in the blank with suitable word :

The speed of sound in a solid is ............... than the speed of sound in air.

Very Short Answers | Q 40.6 | Page 186

Fill in the blank with suitable word.
When the frequency of the sound is increased, the wavelength ____________.

Short Answers | Q 41 | Page 186

What is the vacuum? Explain why, sound cannot travel through vacuum?

Short Answers | Q 42 | Page 186

Explain the term 'amplitude' of a wave. Draw the diagram of a wave and mark its amplitude on it.

Short Answers | Q 43.1 | Page 186

Distinguish between longitudinal and transverse waves.

Short Answers | Q 43.2 | Page 186

Are sound waves longitudinal or transverse?

Short Answers | Q 44 | Page 186

A cricket ball is seen to hit the bat first and the sound of hitting is heard a little later. Why?

Short Answers | Q 45 | Page 186

Explain why, the flash of lightning reaches us first and the sound of thunder is heard a little later.

Short Answers | Q 46 | Page 186

Explain why, the flash of a gun shot reaches us before the sound of the gun shot.

Short Answers | Q 47 | Page 186

Which of the following terms apply to sound waves in air and which to water waves?
Transverse, Rarefaction, Trough, Crest, Compression, Longitudinal

Short Answers | Q 48.1 | Page 186

Name four ways in which sound can be produced.

Short Answers | Q 48.2 | Page 186

Calculate the speed of a sound wave whose frequency is 2 kHz and wavelength 65 cm.

Short Answers | Q 49 | Page 186

If a ringing bicycle bell is held tightly by hand, it stops producing sound. Why?

Short Answers | Q 50 | Page 186

Which object is vibrating when the following sounds are produced?

(i) The sound of a sitar
(ii) The sound of a tabla
(iii) The sound of a tuning fork
(iv) The buzzing of a bee or mosquito
(v) The sound of a flute

Short Answers | Q 51 | Page 186

Give reason for the following :
In most of the cases, we cannot see the vibrations of a sound producing object with our eyes.

Short Answers | Q 52 | Page 186

Describe a simple experiment to show that the prongs of a sound producing tuning fork are vibrating.

Short Answers | Q 53 | Page 186

When we open a gas tap of a few seconds, the sound of escaping gas is heard first but the smell of gas comes later. Why?

Short Answers | Q 54 | Page 186

A sound signal of 128 vibrations per second has a wavelength of 2.7 m. Calculate the speed with which the wave travels.

Short Answers | Q 55 | Page 186

A wave is moving in air with a velocity of 340 m/s. Calculate the wavelength if its frequency is 512 vibrations/sec.

Short Answers | Q 56 | Page 186

Define the 'frequency' and 'time-period' of a wave. What is the relation between the two?

Short Answers | Q 57 | Page 186

Explain why, a ringing bell suspended in a vacuum chamber cannot be heard outside.

Short Answers | Q 58 | Page 186

The frequency of the sound emitted by the loudspeaker is 1020 Hz. Calculate the wavelength of the sound wave in air in cm where its velocity is 340 m/s.

Short Answers | Q 59 | Page 186

What is the difference between a compression and a rarefaction in a sound wave? Illustrate your answer with a sketch.

Long Answers | Q 60.1 | Page 187

What is sound? What type of waves are sound wave in air?

Long Answers | Q 60.2 | Page 187

Describe an experiment to show that sound cannot pass through vacuum.

Long Answers | Q 61.1 | Page 187

How is sound produced? Explain with the help of an example.

Long Answers | Q 61.2 | Page 187

How does sound from a sound producing body travel through air to reach our ears? Illustrate your answer with the help of a labelled diagram.

Long Answers | Q 62.1 | Page 187

An electric bell is suspended by thin wires in a glass vessel and set ringing. Describe and explain what happens if the air is gradually pumped out of the glass vessel.

Long Answers | Q 62.2 | Page 187

Why cannot a sound be heard on the moon? How do astronauts talk to one another on the surface of moon?

Long Answers | Q 63.1 | Page 187

Define the terms 'frequency', 'wavelength' and 'velocity' of a sound wave. What is the relation between them?

Long Answers | Q 63.2 | Page 187

A body vibrating with a time-period of 1/256 s produces a sound wave which travels in air with a velocity of 350 m/s. Calculate the wavelength.

Long Answers | Q 64.1 | Page 187

What are longitudinal waves and transverse waves? Explain with the help of labelled diagrams.

Long Answers | Q 64.2 | Page 187

Give two examples each of longitudinal waves and transverse waves.

Long Answers | Q 65.1 | Page 187

Explain the terms 'compressions' and 'rarefactions' of a wave. What type of waves consist of compressions and rarefactions.

Long Answers | Q 65.2 | Page 187

A worker lives at a distance of 1.32 km from the factory. If the speed of sound in air be 330 m/s, how much time will the sound of factory siren take to reach the worker?

Long Answers | Q 66.1 | Page 187

Explain the terms 'crests' and troughs' of a wave? What type of waves consist of crests and troughs?

Long Answers | Q 66.2 | Page 187

The flash of a gun is seen by a man 3 seconds before the sound is heard. Calculate the distance of the gun from the man (Speed of sound in air is 332 m/s).

Long Answers | Q 67.1 | Page 187

When we put our ear to a railway line, we can hear the sound of an approaching train even when the train is far off but its sound cannot be heard through the air. Why?

Long Answers | Q 67.2 | Page 187

How could you convince a small child that when you speak, it is not necessary for air to travel from you mouth to the ear of listener?

MCQ | Q 68 | Page 187

Which of the following statement best describes frequency?

• the maximum disturbance caused by a wave

• the number of complete vibrations per second

• the distance  between one crest of a wave and the next one

• the distance travelled by a wave per second

MCQ | Q 69 | Page 187

Which of the following vibrates when a musical note is produced by the cymbals in an orchestra?

• stretched strings

• stretched membranes

• metal plates

• air columns

MCQ | Q 70 | Page 187

If the speed of a wave is 340 m/s and its frequency is 1700 Hz, then λ for this wave in cm will be :

• 2

• 0.2

• 20

• 200

MCQ | Q 71 | Page 187

A musical instrument is producing a continuous note. This note cannot be heard by a person having a normal hearing rang. This note must then be passing through.

• water

• wax

• vacuum

• empty vessel

MCQ | Q 72 | Page 187

Which one of the following does not consist of transverse waves?

• light emitted by a CFL

• TV signals from a satellite

• ripples on the surface of a pond

• musical notes of an orchestra

MCQ | Q 72 | Page 187

Sound travels in air :

• if particles of medium travel from one place to another

• if there is no moisture in the atmosphere

• If disturbance moves

• if both, particles as well s disturbance move from one place to another

MCQ | Q 74 | Page 188

In the sound wave produced by a vibrating turning fork shown in the diagram, half the wavelength is represented by :

• AB

• BD

• DE

• AE

MCQ | Q 75 | Page 188

The maximum speed of vibrations which produce audible sound will be in :

• dry air

• sea water

• ground glass

• human blood

MCQ | Q 76 | Page 188

The sound waves travel fastest :

• in solids

• in liquids

• in gases

• in vacuum

MCQ | Q 77 | Page 188

The speeds of sound in four different media are given below. Which of the following is the most likely speed in m/s with which the two under water whales in a sea talk to each other when separated by a large distance?

• 340

• 5170

• 1280

• 1530

MCQ | Q 78 | Page 188

When the pitch of note produced by a harmonium is lowered, then the wavelength of the note :

• decreases

• first decreases and then increases

• increases

• remains the same

MCQ | Q 79 | Page 188

The velocities of sound waves in four media P, Q, R and S are 18,000 km/h, 900 km/h, 0 km/h and 1200 km/h respectively. Which medium could be a liquid substance?

• P

• Q

• R

• S

MCQ | Q 80 | Page 188

Which of the following can produce longitudinal waves as well as transverse waves under different conditions?

• water

• TV transmitter

•  tuning fork

Hots Questions | Q 81 | Page 188

Draw the sketches of two waves A and B such that wave A has twice the wavelength and half the amplitude of wave B.

Hots Questions | Q 82 | Page 188

A device called oscillator is used to send waves along a stretched string. The string is 20 cm long, and four complete waves fit along its length when the oscillator vibrates 30 times per second. For the waves on the strings.

(a) what is their wavelength?
(b) what is their frequency
(c) what is their speed?

Hots Questions | Q 83 | Page 188

Through which of the following materials can sound travel? wood, air, water, steam, ice, hydrogen, steel, diamond.

Hots Questions | Q 84 | Page 188

A sound producing body is at considerable distance from a man. There can be four different media W, X, Y and Z between the sound producing body and the man. The medium X brings the sound to man most quickly whereas medium Z takes the maximum time. The time taken by medium W in bringing sound to man is less than that of X but more than that of Z. The medium Y, however, fails to bring the sound from the sound producing body to the man. Which medium could be the one :
(a) having on fixed shape and no fixed volume?
(b) having a fixed volume but no fixed shape?
(c) having the same composition as that on the moon?
(d) having a fixed shape and a fixed volume?

Hots Questions | Q 85 | Page 188

The longitudinal waves travel in a coiled spring at a rate of 4 m/s. The distance between two consecutive compressions is 20 cm. Find :
(i) Wavelength of the wave (ii) Frequency of the wave

#### Lakhmir Singh solutions for Science for Class 9 Physics Chapter 5 SoundExercise Very Short Answers, Short Answers, Long Answers, MCQ, Hots Questions [Pages 206 - 211]

Very Short Answers | Q 1 | Page 206

Which property of sound leads of the formation of echoes ?

Very Short Answers | Q 2 | Page 206

What name is given to the repetition of sound caused by the reflection of sound waves ?

Very Short Answers | Q 3 | Page 206

What name is given to the persistence of  sound in a big hall or auditorium ?

Very Short Answers | Q 4 | Page 206

Name three devices which work on the reflection of sound.

Very Short Answers | Q 5 | Page 206

What is the other name of a loud-hailer ?

Very Short Answers | Q 6 | Page 206

Name the three characteristics of sound.

Very Short Answers | Q 7 | Page 206

Name the unit used to measure the loudness of sound. Also write its symbol.

Very Short Answers | Q 8 | Page 206

Name the characteristic which helps us distinguish between a man's voice and a woman's voice, even without seeing them.

Very Short Answers | Q 9 | Page 206

How does the pitch of a sound depend on frequency ?

Very Short Answers | Q 10 | Page 206

Name the characteristic of sound which depends on (a) amplitude (b) frequency, and (c) waveform.

Very Short Answers | Q 11 | Page 206

Name the characteristic of sound which can distinguish between the 'notes' (musical sounds) played on a flute and a sitar (both the notes having the same pitch and loudness).

Very Short Answers | Q 12 | Page 206

Name the organs of hearing in our body.

Very Short Answers | Q 13 | Page 206

Name that part of ear which vibrates when outside sound falls on it.

Very Short Answers | Q 14 | Page 206

Name the three tiny bones present in the middle part of ear.

Very Short Answers | Q 15 | Page 206

There are three small bones in the muddle ear – anvil, hammer and stirrup :
(a) Which of these bones is in touch with ear-drum ?
(b) Which of these bones is in touch with oval window ?

Very Short Answers | Q 16 | Page 206

What is the function of three tiny bones in the ear ?

Very Short Answers | Q 17 | Page 207

Name the tube which connects the middle ear to throat.

Very Short Answers | Q 18 | Page 207

Name the nerve which carries electrical impulses from the cochlea of ear to the brain.

Very Short Answers | Q 19 | Page 207

What is the name of passage in outer ear which carries sound waves to the ear-drum ?

Very Short Answers | Q 20 | Page 207

Why should we not put a pin or pencil in our ears ?

Very Short Answers | Q 21 | Page 207

What type of scans are used these days to monitor the growth of developing baby in the uterus of the mother ?

Very Short Answers | Q 22 | Page 207

How is an ultrasound scan for fetus (unborn baby) better than X-ray ?

Very Short Answers | Q 23 | Page 207

What is the name of the device which is used to find the depth of sea (or ocean) by using ultrasonic sound waves ?

Very Short Answers | Q 24 | Page 207

Write the full name of 'SONAR'.

Very Short Answers | Q 25 | Page 207

Name the principle on which a soundboard works.

Very Short Answers | Q 26 | Page 207

Name the device which is used to address a small gathering of people.

Very Short Answers | Q 27 | Page 207

Name the device used by doctors to listen to our heartbeats.

Very Short Answers | Q 28 | Page 207

What is the shape of a soundboard kept behind the speaker on the stage of a big hall ?

Very Short Answers | Q 29 | Page 207

Name two sound absorbing materials (or objects) which can make our big room less echoey.

Very Short Answers | Q 30 | Page 207

Can we hear (a) infrasonic waves (b) ultrasonic waves ?

Very Short Answers | Q 31 | Page 207

What name is given to the sound waves of frequency too low for humans to hear ?

Very Short Answers | Q 32 | Page 207

What name is given to the sound waves of frequency too high for humans to hear ?

Very Short Answers | Q 33 | Page 207

What type of sound waves are produced by a vibrating simple pendulum ?

Very Short Answers | Q 34 | Page 207

What happens to the pitch of a sound if its frequency increases ?

Very Short Answers | Q 35 | Page 207

What happens to the loudness of a sound if its amplitude decreases ?

Very Short Answers | Q 36 | Page 207

What name is given to sound waves of frequencies higher than 20 kHz ?

Very Short Answers | Q 37.1 | Page 207

Fill in the blank with suitable word :
An echo is simply a ................... sound.

Very Short Answers | Q 37.2 | Page 207

Fill in the blank with suitable word :
Pitch of sound depends on ....................

Very Short Answers | Q 37.3 | Page 207

Fill in the blank with suitable word :
Loudness of sound depends on .....................

Very Short Answers | Q 37.4 | Page 207

Fill in the blank with suitable word :
Quality of sound depends on ........................

Very Short Answers | Q 37.5 | Page 207

Fill in the blank with suitable word :
Echoes are caused by the ...................... of sound.

Short Answers | Q 38 | Page 207

On which day, a hot day or a cold day, an echo is heard sooner ? Give reason for your answer.

Short Answers | Q 39 | Page 207

In which medium, air or water, an echo is heard much sooner ? Why ?

Short Answers | Q 40 | Page 207

What is reverberation ? What will happen if the reverberation time in a big hall is too long ?

Short Answers | Q 41 | Page 207

How can reverberations in a big hall or auditorium be reduced ?

Short Answers | Q 42 | Page 207

Why do we hear more clearly in a room with curtains than in a room without curtains ?

Short Answers | Q 43 | Page 207

What is a megaphone ? Name the principle on which a megaphone works.

Short Answers | Q 44 | Page 207

What is a bulb horn ? Name the principle on which a bulb horn works.

Short Answers | Q 45 | Page 207

What is a stethoscope ? Name the principle on which a stethoscope works.

Short Answers | Q 46 | Page 207

What is a  soundboard ? Explain the working of a soundboard with the help of a labelled diagram.

Short Answers | Q 47.1 | Page 207

What is meant by the 'loudness' of sound ? On what factor does the loudness of a sound depend ?

Short Answers | Q 47.2 | Page 207

Draw labelled diagrams to represent (a) soft sound, and (b) loud sound, of the same frequency.

Short Answers | Q 48.1 | Page 207

Explain the term 'pitch' of a sound. On what factor does the 'pitch' of a sound depend ?

Short Answers | Q 48.2 | Page 207

Draw labelled diagrams to represent sound of (a) low pitch, and (b) high pitch, of the same loudness.

Short Answers | Q 49 | Page 208

What is meant by the quality (or timbre) of sound ? On what factor does the quality (or timbre) of a sound depend ?

Short Answers | Q 50 | Page 208

Explain why, if we strike a table lightly, we hear a soft sound but if we hit the table hard, a loud sound is heard.

Short Answers | Q 51 | Page 208

Give one use of ultrasound in industry and one in hospitals.

Short Answers | Q 52 | Page 208

How is it  that bats are able to fly at night without colliding with other objects ?

Short Answers | Q 53 | Page 208

Explain how, bats use ultrasound to catch the prey.

Short Answers | Q 54 | Page 208

Explain how, flaws (or defects) in a metal block can be detected by using ultrasound.

Short Answers | Q 55 | Page 208

Why are the ceilings of concert halls made curved ? Draw a labelled diagram to illustrate your answer.

Short Answers | Q 56 | Page 208

Draw a labelled diagram to show the multiple reflections of sound in a part of the stethoscope tube.

Short Answers | Q 57 | Page 208

What is the range of frequencies associated with (a) infrasound (b) audible sound, and (c) ultrasound ?

Short Answers | Q 58.1 | Page 208

What is the difference between infrasonic waves and ultrasonic waves ?

Short Answers | Q 58.2 | Page 208

Choose the infrasonic waves and ultrasonic waves from the following frequencies :
(i) 10,000 Hz
(ii) 30,000 Hz
(iii) 18 Hz
(iv) 50,000 Hz
(v) 10 Hz

Short Answers | Q 59.1 | Page 208

What is the frequency range of hearing in humans ?

Short Answers | Q 59.2 | Page 208

Which of the following sound frequencies cannot be heard by a human ear ?

(i) 10 Hz
(ii) 100 Hz
(iii) 10,000 Hz
(iv) 15 Hz
(v) 40,000 Hz

Short Answers | Q 60 | Page 208

The echo of a sound is heard after 5 seconds. If the speed of sound in air be 342 m/s, calculate the distance of the reflecting surface.

Short Answers | Q 61 | Page 208

The speed of sound in water is 1500 metres per second. How far away from an under-sea rock should a deep sea diver be so that he can hear his own echo ?

Long Answers | Q 62.1 | Page 208

What is meant by 'reflection of sound' ? What type of surfaces are the best for reflecting sound ?

Long Answers | Q 62.2 | Page 208

Name any two objects which are good reflectors of sound.

Long Answers | Q 62.3 | Page 208

State the laws of reflection of sound.

Long Answers | Q 63.1 | Page 208

What is an echo ? How is echo formed ?

Long Answers | Q 63.2 | Page 208

What is the minimum distance in air required from a sound reflecting surface to hear an echo (at 20°C) ?

Long Answers | Q 63.3 | Page 208

A man standing 825 metres away from a cliff (steep rock) fires a gun. After how long will he hear its echo ? Speed of sound in air is 330 m/s.

Long Answers | Q 64.1 | Page 208

What is ultrasound ? What is the  difference between ordinary sound and ultrasound ?

Long Answers | Q 64.2 | Page 208

Write any three applications (or uses) of ultrasound.

Long Answers | Q 65.1 | Page 208

What are infrasonic waves ? Name two animals which produce infrasonic waves.

Long Answers | Q 65.2 | Page 208

What are ultrasonic waves ? Name two animals which can produce ultrasonic waves.

Long Answers | Q 65.3 | Page 208

The audible range of frequencies of an average human ear is from 20 Hz to 20 kHz. Calculate the corresponding wavelengths. (Speed of sound in air is 344 ms–1)

Long Answers | Q 66.1 | Page 208

Define the following terms : (a) Echolocation (b) Echocardiography, and (c) Ultrasonography.

Long Answers | Q 66.2 | Page 208

Name an animal which navigates and finds food by ecolocation.

Long Answers | Q 66.3 | Page 208

Which of the two produces ultrasonic waves : porpoise or whale ?

Long Answers | Q 67.1 | Page 208

What is sonar ? Explain its use.

Long Answers | Q 67.2 | Page 208

A sonar station picks up a return signal after 3 seconds. How far away is the object ? (Speed of sound in water = 1440 m/s).

Long Answers | Q 68 | Page 208

Draw a neat and labelled diagram of the human ear. With the help of this diagram, explain the construction and working of the human ear.

MCQ | Q 69 | Page 208

In SONAR we use :

• ultrasonic waves

• infrasonic waves

• audible sound waves

MCQ | Q 70 | Page 208

When we change a feeble sound to a loud sound, we increase its :

• frequency

• amplitude

• velocity

• wavelength

MCQ | Q 71 | Page 208

Which kind of sound is produced in an earthquake before the main shock wave begins ?

• ultrasound

• infrasound

• audible sound

• none of the above

MCQ | Q 72 | Page 209

Before playing the orchestra in a musical concert, a sitarist tries to adjust the tension and pluck the strings suitably. By doing so he is adjusting :

• intensity of sound only

• amplitude of sound only

• frequency of the sitar string with the frequency of other musical instruments

• loudness of sound

MCQ | Q 73 | Page 209

'Note' is a sound :

• of a mixture of several frequencies

• of mixture of only two frequencies

• of a single frequency

• always unpleasant to listen to

MCQ | Q 74 | Page 209

A key of mechanical piano is first struck gently and then struck again but much harder this time. In the second case :

• sound will be louder but pitch will not be different

• sound will be louder and the pitch will also be higher

• sound will be louder but pitch will be lower

• both loudness and pitch will remain unaffected

MCQ | Q 75 | Page 209

One of the following can hear infrasound. This one is :

• dog

• bat

• rhinoceros

• humans

MCQ | Q 76 | Page 209

An echo-sounder in a trawler (fishing boat) receives an echo from a shoal of fish 0.4 s  after it was sent. If the speed of sound in water is 1500 m/s, how deep is the shoal ?

• 150 m

• 300 m

• 600 m

• 7500 m

MCQ | Q 77 | Page 209

The speed of highly penetrating ultrasonic waves is :

• lower  than those of audible sound waves

• higher than those of audible sound waves

• much higher than those of audible sound waves

• same as those of audible sound waves

MCQ | Q 78 | Page 209

The ultrasound waves can penetrate into matter to a large extent because they have :

• very high speed

• very high frequency

• very high wavelength

• very high amplitude

MCQ | Q 79 | Page 209

The frequencies of four sound waves are given below. Which of these sound waves can be used to measure the depth of sea by the echo method ?

• 15,000 Hz

• 10 kHz

• 50 kHz

• 10,000 Hz

MCQ | Q 80 | Page 209

Which of the following frequency of sound can be generated by a vibrating simple pendulum as well as by the vibrating vocal cords of a rhinoceros ?

• 5 kHz

• 25 Hz

• 10 Hz

• 15,000 Hz

MCQ | Q 81 | Page 209

Which of the following device does not work on the multiple reflections of sound waves ?

• stethoscope

• hydrophone

• soundboard

• megaphone

MCQ | Q 82 | Page 209

What type of waves are generated by SONAR device fixed to a fishing ship ?

• water waves

• sound waves

• infrared waves

MCQ | Q 83 | Page 209

We can distinguish between the musical sounds produced by different singers on the basis of the characteristic of sound called :

• frequency

• timbre

• pitch

• loudness

MCQ | Q 84 | Page 209

At 20°C, the minimum distance of a person from a sound reflecting surface to hear an echo is :

• 12.2 m

• 17.2 m

• 15.2 m

• 34.4 m

Hots Questions | Q 85 | Page 209

The drawing shows a ship 800 m from a cliff. A gun is fixed on the ship. After 5 seconds the people at the front of the ship hear the sound of the gun again.

(a) What is the name of this effect ?
(b) What happens to the sound at the cliff ?
(c) How far does the sound travel in 5 seconds ?
(d) Calculate the speed of sound.

Hots Questions | Q 86 | Page 210

Consider the following sound waves marked A, B, C and D.

(a) Which two waves represent sounds of the same loudness but different pitch ?
(b) Which two waves represent sounds of the same frequency but different loudness ?
(c) State whether all these sound waves have been produced by the same vibrating body or different vibrating bodies ?
(d) Which vibrating body/bodies could have generated the sound waves shown here ?

Hots Questions | Q 87 | Page 210

In an experiment, Anhad studies sound waves. He sets up a loudspeaker to produce sound as shown below :

Anhad adjusts the signal to the loudspeaker to give a sound of frequency 200 Hz.
(a) What happens to the air in-between Anhad and the loudspeaker ?

Hots Questions | Q 88 | Page 210

Figure X shows a trace of a sound wave produced by a particular tuning fork :

(a) On the graph paper given in Figure Y, draw a trace of the sound wave which has a higher frequency than that shown in figure X.
(b) On the graph paper show in Figure Z, draw a trace of the sound wave which has a larger amplitude than that shown in Figure X.

Hots Questions | Q 89 | Page 210

Three different vibrating objects produce three-types of sounds X, Y and Z. Sounds X and Y cannot be heard by a man having normal range of hearing but sound Z can be heard easily. The sound X is used in hospitals to break kidney stones of a patient into fine grains which then get flushed out with urine. The sound Y is similar to that which is produced during an earthquake before the main shock wave is generated.

(a) What type of sounds are (i) X (ii) Y, and (iii) Z ?
(b) Name one device which can produce sound like X.
(c) Name one device in a science laboratory which can produce sound like Y.
(d) Name one device in our homes which can produce sound like Z.
(e) What is the frequency range of sounds like Z ?

Hots Questions | Q 90.1 | Page 211

A man is kidnapped, blindfolded and imprisoned in a big room. How could the man tell if he was in : a city

Hots Questions | Q 90.2 | Page 211

A man is kidnapped, blindfolded and imprisoned in a big room. How could the man tell if he was in : a village

Hots Questions | Q 90.3 | Page 211

A man is kidnapped, blindfolded and imprisoned in a big room. How could the man tell if he was in : a bare room

Hots Questions | Q 90.4 | Page 211

A man is kidnapped, blindfolded and imprisoned in a big room. How could the man tell if he was in : a furnished room

## Lakhmir Singh solutions for Science for Class 9 Physics chapter 5 - Sound

Lakhmir Singh solutions for Science for Class 9 Physics chapter 5 (Sound) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CBSE Science for Class 9 Physics solutions in a manner that help students grasp basic concepts better and faster.

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Concepts covered in Science for Class 9 Physics chapter 5 Sound are Production of Sound, Propagation of Sound, Sound Needs a Medium to Travel, Sound Waves Are Longitudinal Waves, Speed of Sound in Different Media, Echo, Reverberation, Uses of Multiple Reflection of Sound, Range of Hearing in Humans, Applications of Ultrasound - SONAR, Structure of the Human Ear (Auditory Aspect Only), Characteristics of a Sound Wave, Sound (Numerical), Reflection of Sound.

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