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Science Do as directed; [1 M ]

Sound · CBSE STD 9 (CBSE - English Medium). 90 questions.

Questions · Page 2 of 2

Do as directed; [1 M ]

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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