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NIOS Class 10 Science and Technology Chapter 18 Sound and communication
Also, you can read the NIOS book online in these sections Solutions by Expert Teachers as per National Institute of Open Schooling (NIOS) Book guidelines. These solutions are part of NIOS All Subject Solutions. Here we have given NIOS Class 10 Science and Technology Chapter 18 Sound and communication, NIOS Secondary Course Science and Technology Solutions for All Chapters, You can practice these here.
Sound and communication
Chapter: 18
INTEXT QUESTIONS 18.1
1. Which sound wave will have its crests farther apart from each other – a wave with frequency 100 or a wave with frequency 500?
Ans: The wave with frequency 100 will have its crests farther apart as its wavelength will be higher. For sound waves, the velocity ‘v’ is equal to the product of wavelength and frequency (v = n × λ or v/n = λ) and thus wavelength and frequency are inversely proportional. So for the same velocity, the lower
frequency waves will have a larger wavelength. Therefore, for the wave with a frequency of 100 Hz, will have a higher wavelength and the crests will be farther apart compared to the wave with frequency 500 Hz.
2. If the velocity of sound is 330 metres per second (ms–1), what will be the wavelength if the frequency is 1000 Hertz?
Ans: Wavelength = 0.33 metre.
3. What is the approximate audible range of frequency for humans?
Ans: About 20 Hz to 20KH.
INTEXT QUESTIONS 18.2
1. Does a wave transfer energy or material?
Ans: A wave transfers energy. Even when the material is displaced, it’s temporary and it comes back to its normal position such as in case of a ripple in water.
2. How do mechanical and electromagnetic waves differ?
Ans: Medium is essential for propagation of mechanical waves. Electromagnetic waves can travel through vacuum as well as any medium. But they lose energy in liquids and solids very fast. Sound waves can travel through liquids and solids with much lower losses. The velocity of sound waves is highest in solids (a few thousand metres per second). The velocity of electromagnetic waves in contrast is extremely high: about 3 lakh km per second.
3. What is the difference between a transverse and longitudinal wave?
Ans: In a transverse wave, the direction of propagation of the wave (the direction of energy-transfer) is perpendicular to the direction of oscillations whereas in longitudinal waves, particles of the medium vibrate parallel to the direction of wave propagation.
4. Do transverse waves form in solid?
Ans: Yes, The sound waves travel in solids.
INTEXT QUESTIONS 18.3
1. What is the unit to measure sound intensity?
Ans: The unit to measure sound level is decibel. It’s one tenth of a bel. Actually the decibel is a comparative scale. For us, the reference is fixed at the just audible sound so we normally speak of sound level in decibels.
2. Why do they have many holes at the side of a flute lengthwise?
Ans: Flute is an organ pipe in which air columns vibrate. More the length of the air column, more the wavelength of sound produced and hence loss the frequency. Holes are provided by the side of the flute so that by closing the holes length of the vibrating air column may be changed.
INTEXT QUESTIONS 18.4
1. Give three examples of devices that make use of microphones or speakers or both.
Ans: Telephone, Radio and Television.
2. In a condenser microphone, what will happen if the diaphragm is made very heavy?
Ans: In a condenser microphone, if the diaphragm is made very heavy, the inertia of the diaphragm will be higher. This means it will be difficult for the diaphragm to move rapidly. Its movement can’t be fast enough and so it will not be possible to reproduce very high frequencies.
INTEXT QUESTIONS 18.5
1. List some uses of satellites.
Ans: Satellites are useful in communication, surveying, photographing of geographical features of earth and astronomy.
2. If a satellite equipped with cameras remains fixed at one height above ground even as earth rotates and moves in its orbit, what is its possible use?
Ans: If the satellite is stationary but earth below it keeps moving, the view will keep changing. Thus without the satellite moving, the satellite cameras will see the whole surface of earth facing it.
3. Arrange the low orbit, geostationary and polar satellites in decreasing order of altitude above Earth (the highest one comes first).
Ans: The geostationary, polar and low satellites. The geostationary satellites are the highest at about 36,000 km. The Polar satellites are lower than them and the Low Earth Satellites (160-1400 km) are the lowest.
4. Which of the satellites are preferred for communication application?
Ans: Geostationary satellites are preferred for communication application. This is because from earth they appear fixed at the same place. Thus if the antennas are directed towards them once, we don’t have to worry about tracking them.
| TERMINAL EXERCISE |
1. Fill in the blanks:
(i) Sound travels at a ____________ velocity than light.
Ans: Lower.
(ii) When there is lightning, we first ____________ and then hear it.
Ans: Saw
(iii) SONAR makes use of ____________ waves while RADAR makes use of ____________ waves.
Ans: Ultrasonic and infrasonic.
(iv) Microphone converts sound into ____________ while speaker converts electrical signal into ____________.
Ans: Electrical signs and mechanical energy.
2. Multiple choice type questions:
(i) Which satellite will see a wider area on Earth?
(a) A low earth orbit satellite.
(b) A high earth orbit satellite.
(c) A medium earth orbit satellite.
Ans: (b) A high earth orbit satellite.
(ii) India’s first self launched satellite was.
(a) IRS.
(b) Aryabhatta.
(c) Rohini.
(d) INSAT.
Ans: (b) Aryabhatta.
(iii) For the same velocity, will a higher frequency of a sound wave mean
(a) Higher wavelength.
(b) Lower wavelength.
(c) The same wavelength.
Ans: (a) Higher wavelength.
(iv) Sound travels fastest in.
(a) Solid.
(b) Liquid.
(c) Gas.
Ans: (a) Solid.
(v) The most suitable medium for RADAR would be.
(a) Gas.
(b) Liquid.
(c) Solid.
Ans: (c) Solid.
3. Why can’t we hear each other on Moon?
Ans: Sound needs a medium to be transmitted. Thus a person on the moon cannot hear another person on the moon. This is because there is no air on the moon and it is a vacuum( no medium). Thus there is no medium for sound waves to travel.So two persons cannot hear their voice on moon.
4. Describe 2 experiments to show that sound has vibrations associated with it.
Ans: 2 experiments to show that sound has vibrations associated are mentioned below:
(i) Aluminium hanger experiment.
(ii) Tuning fork experiment.
5. What is the relationship between velocity, wavelength and frequency?
Ans: Do yourself.
6. State 3 differences between sound waves and microwaves.
Ans: 3 difference between sound waves and microwaves are mentioned below:
Sound waves:
(i) Sound waves, on the other hand, are compressions and decompressions of air. Our ears are sensitive to the latter, but not to the former.
(ii) Sound wave travel at about 300 m/s (depending on the medium) whereas Electromagnetic wave travel at around 300,000,000 m/s i.e. the speed of light.
Microwaves.
(ii) Microwaves are a form of electromagnetic waves, which means they’re oscillations of electric and magnetic fields.
(ii) Micro waves travels through electromagnetic radiation (EMR).
7. What are the differences between longitudinal and transverse sound waves?
Ans: The differences between longitudinal and transverse sound waves:
8. Will sound move faster in solid or air?
Ans: Sound travels fastest through solids.This is because molecules in a solid medium are much closer together than those in a liquid or gas, allowing sound waves to travel more quickly through it.
9. What is the basic difference between noise and music?
Ans: The basic difference between noise and music are mentioned below:
Music:
(i) Music is a sound which produces a pleasing sensation while noise is an unwanted and unpleasant sound.
(ii) Music is produced by musical instruments like piano, guitar, flute, etc.
Noise:
(i) Noise is produced by the horns of vehicles, crackers, machines, etc.
(ii) Noise is an unwanted sound that does not have any kind of rhythm or beat or melody.
10. What makes your voice appear more musical when you sing in a bathroom?
Ans: Bathroom tiles don’t absorb sound, so when you sing, your voice bounces around the cubicle and sounds more powerful. Then, there’s the size of your concert hall. Unless your patron paid you extra well this month, the shower is usually a fairly small space, meaning your singing sounds louder and gains a little bass.
11. How is active SONAR different from passive SONAR?
Ans: “Sonar” can refer to one of two types of technology: passive sonar means listening for the sound made by vessels; active sonar means emitting pulses of sounds and listening for echoes. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of “targets” in the water.
12. What are the relative merits of SONAR and RADAR? Why is it better to use SONAR in water?
Ans: There is a benefit of using the sonar as compared to radar in the water. As the radar when transfer the signal in water its range is small because of the absorbing of the water but in sonar it doesn’t see.
13. How does SONAR help in estimating the distance of an object?
Ans: SONAR is used for the measurements of the distance between the object which is at a place in under water by reflecting the sound wave. In this case when the sound wave is fell on the object and back to it the. Calculating the time according to distance covered we measure the existence of object under water.
