Gujarat Board GSEB Textbook Solutions Class 8 Science Chapter 13 Sound Textbook Questions and Answers, Notes Pdf.

Gujarat Board Textbook Solutions Class 8 Science Chapter 13 Sound

Gujarat Board Class 8 Science Sound Textbook Questions and Answers

Choose the correct answer
Question 1.
Sound can travel through:
(a) gases only
(b) solids only
(c) liquids only
(d) solids, liquids, and gases.
Answer:
(d) solids, liquids, and gases.

Question 2.
Voice of which of the following is likely to have a minimum frequency?
(a) Baby girl
(b) Baby boy
(c) A man
(d) A woman
Answer:
(a) Baby girl.

Question 3.
In the following statements, tick ‘T’ against those which are true, and ‘F’ against those which are false:
(a) Sound cannot travel in a vacuum.
(b) The number of oscillations per second of a vibrating object is called its time period.
(c) If the amplitude of vibration is large, the sound is feeble.
(d) For human ears, the audible range is 20 Hz to 20,000 Hz.
(e) The lower the frequency of vibration, the higher is the pitch.
(f) Unwanted or unpleasant sound is termed as music.
(g) Noise pollution may cause partial hearing impairment.
Answer:
(a) True
(b) False
(c) False
(b) True
(e) False
(f)False
(g) True.

Question 4.
in the blanks with suitable words:
(a) Time taken by an object to complete one oscillation is called ………
(b) Loudness is determined by the ………… of vibration.
(c) The unit of frequency is ………..
(d) Unwanted sound is called ……….
(e) The shrillness of a sound is determined by the ……….. of vibration.
Answer:
(a) time period
(b) amplitude
(c) hertz
(d) noise
(e) frequency

Question 5.
A pendulum oscillates 40 times in 4 seconds. Find its time period and frequency.
Answer:
Number of oscillations = 40
Total time = 4 seconds
Time taken to complete one oscillation 4 1
= (frac {4}{40}) = (frac {1}{10}) = 0.1 second
So time period = 0.1 second.

Question 6.
The sound from a mosquito is produced when it vibrates its wings at an average rate of 500 vibrations per second, what is the time period of the vibration?
Answer:
Total vibrations = 500
Time taken = 1 second
Time taken to complete one vibration
= (frac {1}{500}) = 0.002 seconds.
So time period = 0.002 seconds.

Question 7.
Identify the part which vibrates to produce sound in the following instruments.
(a) Dholak
(b) Sitar
(c) Flute
Answer:
(a) Stretched membrane
(b) Strings
(c) Air column.

Question 8.
What is the difference between noise and music? Can music become noise sometimes?
Answer:
The sound which is unpleasant for our ears is called noise while music is the sound that is pleasant for our ears. Music becomes noise sometimes when it crosses the bearable range of sound for our ears.

Question 9.
List sources of noise pollution in your surroundings.
Answer:
Sources of noise pollution: Honking of horns, loudspeakers, loud sounds of machines in factories, loud sounds of T.V., radio, domestic appliances etc.

Question 10.
Explain in what way noise pollution is harmful to humans.
Answer:
Harmful effects of noise pollution:

• It causes deafness
• It causes mental illness
• It causes headache and high blood pressure

Question 11.
Your parents are going to buy a house. They have been offered one on the roadside and another three lanes away from the roadside. Which house would you suggest to your parents to buy? Explain your answer.
Answer:
I would suggest my parents buy the house three lanes away from the roadside. This house would safeguard our health and peace of mind.

Question 12.
Sketch larynx and explain its function in your own words.
Answer:
The larynx is also known as the voice box. It has vocal cords which have air column vibrating in them, which cause sound in humans.

Question 13.
Lightning and thunder take place in the sky at the same time and at the same distance from us. Lightning is seen earlier and thunder is heard later. Can you explain why?
Answer:
The speed of light is more than that of sound. Due to more speed, the light reaches us before the sound does. So lightning is seen earlier and thunder is heard later.