Lakhmir Singh solutions for Physics (Science) [English] Class 9 ICSE chapter 5 - Sound [Latest edition]

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

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

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

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

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

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

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

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

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

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

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

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.

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?

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?

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.

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

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

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

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

Fill in the blanks with suitable words .

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

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

Fill in the blank with suitable word : 

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

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

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

Distinguish between longitudinal and transverse waves.

Are sound waves longitudinal or transverse?

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

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

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

Name four ways in which sound can be produced.

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

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

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

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

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?

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

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

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

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

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

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

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.

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.

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

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

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.

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

Give two examples each of longitudinal waves and transverse waves.

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

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?

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

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).

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?

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?

Which of the following statement best describes frequency?

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

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 :

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.

Sound travels in air :

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

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

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

The sound waves travel fastest :

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?

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

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?

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

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

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?

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

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?

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

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

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

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).

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 ?

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.

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

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

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

What is the difference between infrasonic waves and ultrasonic waves ?

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 

What is the frequency range of hearing in humans ?

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 

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.

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 ?

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

Name any two objects which are good reflectors of sound.

State the laws of reflection of sound.

What is an echo ? How is echo formed ?

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

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.

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

Write any three applications (or uses) of ultrasound.

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

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

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)

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

Name an animal which navigates and finds food by ecolocation.

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

What is sonar ? Explain its use.

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).

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.

In SONAR we use:

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

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

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 :

'Note' is a sound :

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

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

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 ?

The speed of highly penetrating ultrasonic waves is :

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

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 ?

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 ?

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

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

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

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

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.

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 ?

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 ?
(b) Explain how Anhad receives sound in both ears.

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.

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 ?

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

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

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

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