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Science Do as directed; [1 M ]

Sound · Jharkhand Board (JAC) STD 9 (Jharkhand - English Medium). 90 questions.

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90 questions · self-marked practice — reveal the answer and mark yourself.

Question 11 Mark
A tuning fork has a number $256$ marked on it. What does this number signify$?$
Answer
The number $256$ on tuning fork signifies the frequency of tuning fork.
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Question 21 Mark
What is the minimum distance in air required from a sound reflecting surface to hear an echo $($at $20^{\circ} \mathrm{C})?$
Answer
The minimum distance in air required from a sound reflecting surface to hear an echo $($at $20^{\circ} \mathrm{C} )$ is $17.2$ metrers.
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Question 31 Mark
What name is given to those aircrafts which fly at speeds greater than the speed of sound?
Answer
Supersonic aircrafts.
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Question 61 Mark
What is the general name of the waves consisting of: Compressions and rarefactions?
Answer
Longitudinal waves.
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Question 101 Mark
Define the ‘frequency’ and ‘time-period’ of a wave. What is the relation between the two?
Answer
The number of complete waves (or cycles) produced in one second is called frequency of the wave. The time required to produce one complete wave (or cycle) is called time-period of the wave. The time taken to complete one vibration is called time-period. Relation between time-period an frequency of a wave is: $\text{Frequency}=\frac{1}{\text{time period}}$
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Question 111 Mark
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 $
$(v) 10\ Hz$
Answer
Infrasonic waves: $10\ Hz, 18\ Hz$
Ultrasonic waves: $30,000\ Hz, 50,000\ Hz$
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Question 121 Mark
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).
Answer
Quality or timbre.
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Question 131 Mark
In which medium, air or water, an echo is heard much sooner? Why?
Answer
An echo is heard sooner in water because the speed of sound in water is higher than the speed of sound in air.
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Question 141 Mark
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?
Answer
The conclusion from the observation is that the prongs of tuning fork are vibrating, and the vibrating prongs carry energy which gets transmitted to surrounding medium.
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Question 151 Mark
Name that part of ear which vibrates when outside sound falls on it.
Answer
Ear drum starts vibrating when outside sound falls on it.
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Question 181 Mark
If $20$ waves are produced per second, what is the frequency in hertz$?$
Answer
The frequency in hertz is equal to the number of waves produced per second. In this case, $20$ waves are produced per second, so the frequency of sound waves is $20$ hertz.
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Question 201 Mark
Name the principle on which a soundboard works.
Answer
Soundboard works on the principle of reflection of sound.
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Question 221 Mark
Is the speed of sound more in water or in steel?
Answer
Speed of sound is more in steel (solid medium) as compared to water (liquid medium).
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Question 231 Mark
Explain why, the flash of lightning reaches us first and the sound of thunder is heard a little later.
Answer
Light travels much faster than sound. Due to this, the flash of lightning is seen first and the sound of thunder is heard a little later.
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Question 241 Mark
Name the device used by doctors to listen to our heartbeats.
Answer
A stethoscope, based on the principle of reflection of sound, is used by doctors to listen to our heartbeats.
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Question 251 Mark
Out of solids, liquids and gases: In which medium sound travels fastest?
Answer
Sound travels fastest in solids.
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Question 271 Mark
What name is given to the repetition of sound caused by the reflection of sound waves?
Answer
Echo is repetition of sound caused by the reflection of sound waves.
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Question 281 Mark
If you want to hear a train approaching from far away, why is it more convenient to put the ear to the track?
Answer
It is more convenient to put the ear to the track to hear a train approaching from far away because sound travels faster in solids than in air.
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Question 291 Mark
Name the type of waves which are used by astronauts to communicate with one another on moon (or in outer spece).
Answer
Radio waves are used to communicate with one another on moon.
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Question 311 Mark
Which property of sound leads of the formation of echoes?
Answer
The reflection of sound leads to formation of echoes.
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Question 331 Mark
Can we hear $(a)$ infrasonic waves $(b)$ ultrasonic waves$?$
Answer
No, we cannot hear infrasonic waves and ultrasonic waves. That’s because the frequencies of both these waves fall beyond the human audible range of frequencies.
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Question 351 Mark
What is the name if the device which is used to find the depth of sea (or ocean) by using ultrasonic sound waves$?$
Answer
$SONAR$ is used to find the depth of sea by using ultrasonic sound waves.
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Question 361 Mark
What is the time-period of a tuninh fork whose frequency is $200\ Hz?$
Answer
$\text{Frequency}=\frac{1}{\text{Time period}}$ $\text{Frequency}=200\text{Hz}$ $\text{Time period}=\frac{1}{\text{Frequency}}$ $=\frac{1}{200}=5\times10^{-3}\ \text{sec}$
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Question 381 Mark
In which medium sound travels faster: air or iron?
Answer
Sound travels faster in iron (being a solid medium).
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Question 391 Mark
In which medium sound travels fastest: air, water or steel?
Answer
Sound travels fastest in steel (solid medium).
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Question 401 Mark
Can sound travel through $(a)$ iron, and $(b)$ water$?$
Answer
Yes, sound can travel through iron and as well as water.
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Question 411 Mark
What is meant by supersonic speed?
Answer
Supersonic speed refers to the speed of an object which is greater than the speed of sound.
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Question 421 Mark
Name the three tiny bones present in the middle part of ear.
Answer
The three tiny bones present in the middle part of ear are: anvil, hammer and stirrup.
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Question 431 Mark
What happens to the pitch of a sound if its frequency increase?
Answer
As the frequency increases the pitch of the sound also increases.
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Question 441 Mark
Which of the following travels slowest in air and which one fastest?
Supersonic aircraft, Light, Sound.
Answer
  • Slowest - Sound
  • Fastest - light
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Question 451 Mark
What type of scans are used these days to monitor the growth of developing baby in the uterus of the mother?
Answer
Ultrasound scans are used to monitor the growth of developing baby in the uterus of the mother.
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Question 461 Mark
What name is given to the persistence of sound in a big hall or auditorium?
Answer
The persistence or sound in a big hall or auditorium is called reverberation.
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Question 471 Mark
What should an object do to produce sound?
Answer
An object should vibrate in order to produce sound.
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Question 481 Mark
There are three small bones in the middle ear-anvil, hammer and stirrup: Which of these bones is in touch with oval window?
Answer
Stirrup.
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Question 491 Mark
What is the shape of a soundboard kept behind the speaker on the stage of a big hall?
Answer
Soundboard is a concave board which is kept behind the speaker on the stage of a big hall.
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Question 501 Mark
Name three devices which work on the reflection of sound.
Answer
  1. Megaphone and bulb horn.
  2. Stethoscope.
  3. Soundboard.
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Question 511 Mark
Name one solid, one liquid and one gas through which sound can travel.
Answer
  • Solid - table.
  • Liquid - water.
  • Gas - air.
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Question 521 Mark
What is the name of passage in outer ear which carries sound waves to the ear-drum?
Answer
Ear canal.
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Question 531 Mark
How is an ultrasound scan for fetus (unborn baby) better than $X$-ray?
Answer
An ultrasound scan for fetus is better than $X$-rays because $X$-rays can damage the delicate body cells of the fetus.
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Question 541 Mark
Name the two types of waves which can be generated in a long flexible spring (or slinky).
Answer
Transverse and Longitudinal waves.
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Question 551 Mark
Name the device which is used to produce sound in laboratory experiments.
Answer
Tuning fork is used to produce sound in laboratory experiments.
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Question 561 Mark
Which of the following is the speed of sound in copper and which in aluminium?
  1. $5100\ m/s$
  2. $1500\ m/s$
  3. $3750\ m/s$
Answer
  1. Speed of sound in copper $= 3750\ m/s$
  1. Speed of sound in aluminium $= 5100\ m/s$
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Question 571 Mark
Which of the following terms apply to sound waves in air and which to water waves? Transverse, Rarefaction, Trough, Crest, Compression, Longitudinal.
Answer
Sound waves in air: Longitudinal, Compression, Rarefaction.
Water waves: Transverse, Crest, Trough.
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Question 581 Mark
Which term is used to denote a speed greater than the speed of sound?
Answer
Supersonic is used to denote a speed greater than the speed of sound.
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Question 601 Mark
Out of solids, liquids and gases:
In which medium sound travels slowest?
Answer
Sound travels slowest in gases.
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Question 611 Mark
Calculate the frequency of a wave whose time-period is $0.02s$.
Answer
$\text{Frequency}=\frac{1}{\text{Time period}}$ $=\frac{1}{0.02}=50\text{Hz}$
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Question 621 Mark
What will be the change in the wavelength of a sound wave in air if its frequency is doubled?
Answer
Velocity of sound = Frequency $\times $ wavelength Speed of sound in air is constant.
Hence, frequency $\times $ wavelength = constant If frequency is doubled, wavelength is reduced to half.
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Question 631 Mark
What name is given to the sound waves of frequency too high for humans to hear?
Answer
Ultrasonic sounds.
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Question 641 Mark
What is the function of three tiny bones in the ear?
Answer
The function of three tiny bones in the ear is to increase the strength of vibrations coming from the ear drum before passing them onto the inner ear.
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Question 651 Mark
What is the name of the strings which vibrate in our voice box when we talk?
Answer
Vocal cords vibrate in our voice box when we talk.
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Question 661 Mark
Name the characteristic of sound which depends on (a) amplitude (b) frequency, and (c) waveform.
Answer
  1. Loudness.
  2. Pitch.
  3. Timbre.
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Question 671 Mark
Name the unit used to measure the loudness of sound. Also write its symbol.
Answer
The loudness of sound is measured in decibel. Its symbol is $dB$.
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Question 681 Mark
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.$
Answer
The sound frequencies that cannot be heard by a human ear are $10\ Hz, 15\ Hz$ and $40,000\ Hz$.
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Question 701 Mark
What is the speed of sound:
  1. In air?
  2. In water?
  3. In iron?
Answer
Speed of sound (at $20^{\circ}C$) in:
  1. Air $= 344\ m/s$
  2. Water $= 1498\ m/s$
  3. Iron $= 5130\ m/s$
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Question 711 Mark
Name an animal which navigates and find food by echolocation.
Answer
Bat navigates and finds its food by echolocation.
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Question 721 Mark
State one observation from everyday life which shows that sound travels much more slow than light.
Answer
It is common observation that in the rainy season, the flash of lightning is seen first and the sound of thunder is heard a little later. That’s because, speed of light is very high as compared to speed of sound in air.
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Question 731 Mark
Name the characteristic which helps us distinguish between a man’s voice and woman’s voice, even without seeing them.
Answer
Pitch helps us to distinguish between a man’s voice and a woman’s voice, even without seeing them.
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Question 741 Mark
Name two sound absorbing materials (or objects) which can make our big room less echoey.
Answer
Curtains and carpets can make our big room less echoey.
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Question 781 Mark
Name the nerve which carries electrical impulses from the cochlea of ear to the brain.
Answer
Auditory nerve.
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Question 791 Mark
Name the device which is used to address a small gathering of people.
Answer
A megaphone is used to address a small gathering of people.
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Question 811 Mark
State the general name of the waves on which the particles of the medium vibrate: In the same direction as wave.
Answer
Longitudinal waves.
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Question 821 Mark
What happens to the loudness of a sound if its amplitude decrease?
Answer
The loudness decreases with the decrease in the amplitude of sound.
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Question 831 Mark
In which medium sound travels faster: air or hydrogen?
Answer
Sound travels faster in hydrogen (speed of sound in hydrogen is $1284\ m/s$).
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Question 841 Mark
There are three small bones in the middle ear-anvil, hammer and stirrup: Which of these bones is in touch with ear-drum?
Answer
Hammer.
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Question 851 Mark
State the general name of the waves on which the particles of the medium vibrate: At right angles to the direction of wave.
Answer
Transverse waves.
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Question 861 Mark
Explain why, the flash of a gun shot reaches us before the sound of the gun shot.
Answer
Light travels much faster than sound. Due to this, the flash of gunshot is seen first and the sound of gunshot is heard a little later.
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Question 871 Mark
A stone is dropped on the surface of water in a pond. Name the type of waves produced.
Answer
Transverse (water) waves.
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Question 891 Mark
How does the pitch of a sound depend on frequency?
Answer
Pitch of a sound is directly proportional to frequency. Higher the frequency, higher is the pitch of the sound.
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Question 901 Mark
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?
Answer
Transverse waves.
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