CBSE · NCERT · Class 8 Science · Chapter 10

NCERT Solutions: Class 8 Science Chapter 10 - Sound

13 textbook Q&A13 verifiedFree Content

Chapter-wise NCERT intext questions and exercise answers for Sound, grounded in the official textbook.

Questions are taken verbatim from the NCERT textbook; answers were grounded against the chapter's content during generation. Items needing review are marked.
Sections in this chapter
Exercises 13
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1Exercises13 questions
Q.1Sound can travel throughv
  1. a. gases only
  2. b. solids only
  3. c. liquids only
  4. d. solids, liquids and gases
Answer:

(d) solids, liquids and gases.

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Q.2Voice of which is likely to have minimum frequency?v
  1. a. Baby girl
  2. b. Baby boy
  3. c. A man
  4. d. A woman
Answer:

(c) A man.

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Q.3Mark true or false for statements about vacuum, oscillations, amplitude, audible range, pitch, music and hearing.v
Answer:

(a) True (b) False (c) False (d) True (e) False (f) False (g) True.

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Q.4Fill in the blanks about time period, loudness, frequency unit, unwanted sound and shrillness.v
Answer:

(a) time period (b) amplitude (c) hertz (Hz) (d) noise (e) frequency.

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Q.5A pendulum oscillates 40 times in 4 seconds. Find its time period and frequency.v
Solution

Frequency $=40/4=10$ oscillations per second. Time period $=1/10=0.1$ s.

Answer:

Frequency $=10$ Hz and time period $=0.1$ s.

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Q.6A mosquito vibrates wings at 500 vibrations per second. What is the time period?v
Solution

Time period $=1/500=0.002$ s.

Answer:

$0.002$ s.

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Q.7Identify the vibrating part in dholak, sitar and flute.v
Answer:

Dholak: stretched membrane. Sitar: strings. Flute: air column.

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Q.8What is the difference between noise and music? Can music become noise?v
Answer:

Music is pleasant sound; noise is unwanted or unpleasant sound. Music can become noise if it is too loud or disturbing.

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Q.9List sources of noise pollution in your surroundings.v
Answer:

Vehicle horns, loudspeakers, firecrackers, construction machines, factories, loud televisions and generators.

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Q.10How is noise pollution harmful?v
Answer:

It can cause headache, stress, lack of sleep, high blood pressure, poor concentration and partial hearing impairment.

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Q.11Which house should be preferred: roadside or three lanes away? Explain.v
Answer:

The house three lanes away should be preferred because it will have less traffic noise and air pollution.

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Q.12Sketch larynx and explain its function.v
Answer:

The larynx or voice box lies at the upper end of the windpipe. It contains vocal cords which vibrate when air passes through them and produce sound.

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Q.13Why is lightning seen before thunder is heard?v
Answer:

Light travels much faster than sound, so light from lightning reaches us before the sound of thunder.

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Next: Ch.11