Samacheer Kalvi 8th Science Unit 6 Book Back Answers:

Samacheer Kalvi 8th Standard New Science Book Back 1 Mark and 2 Mark Question & Answers PDF uploaded and available below. Class 8 New Syllabus 2021 to 2022 Book Back Question & Answer available for both English and Tamil Mediums. Class 8th Science Book Unit 6 – Sound Answers/Solutions are provided on this page. 8th Std Science Book consists of 23 units, All Science Book Back One, and Two Mark Solutions are given below.

Check Unit wise and  Samacheer Kalvi 8th Science Book Back Solutions Answers PDF format for Free Download. English, Tamil, Maths, Science, and Social Science Book Back Question and Answer is available in PDF. Class 8th Standard Science Book Back Answers PDF. Check Science book back Answers below. See below for the 8th New Science Syllabus Book Back guide/Answers free PDF download:

Samacheer Kalvi 8th Science Book Back Solutions PDF:

8th Science Subject 1 Mark and 2 Mark Solutions PDF available below. Click the Download option to download the book back 1 Mark & 2 Mark questions and answers. Take the printout and use it for exam purposes. Samacheer Kalvi 8th Science Unit 6 Answers are given below.

Science Book Back Answers

Unit 6 – Sound

I. Choose the best answer:

1. Sound waves travel very fast in …………..
(a) air
(b) metals
(c) vacuum
(d) liquids
Answer:
(b) metals

2. Which of the following are the characteristics of vibrations?
(i) Frequency
(ii) Time period
(iii) Pitch
(iv) Loudness

(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (i) and (iv)
Answer:
(c) (iii) and (iv)

3. The amplitude of the sound wave decides it’s ……………
(a) speed
(b) pitch
(c) loudness
(d) frequency
Answer:
(c) loudness

4. What kind of musical instrument is a sitar?
(a) String instrument
(b) Percussion instrument
(c) Wind instrument
(d) None of these
Answer:
(a) String instrument

5. Find the odd one out.
(a) Harmonium
(b) Flute
(c) Nadaswaram
(d) Violin
Answer:
(d) Violin

Reason:
Violin is a stringed instrument. Other are wind or reed instruments.

6. Noise is produced by …………..
(a) vibrations with high frequency
(b) regular vibrations.
(c) regular and periodic vibrations
(d) irregular and non-periodic vibrations.
Answer:
(d) irregular non-periodic vibrations

7. The range of audible frequency for the human ear is …………..
(a) 2 Hz to 2000 Hz
(b) 20 Hz to 2000 Hz
(c) 20 Hz to 20000 Hz
(d) 200 Hz to 20000 Hz
Answer:
(c) 20 Hz to 20000 Hz

8. If the amplitude and frequency of a sound wave are increased, which of the following is true?
(a) Loudness increases and pitch is higher
(b) Loudness increases and pitch is unchanged
(c) Loudness increases and pitch is lower
(d) Loudness decreases and pitch is lower
Answer:
(a) Loudness increases and pitch is higher

II. Fill in the blanks:

1. Sound is produced by …………
2. The vibrations of a simple pendulum are also known as …………
3. Sound travels in the form of …………
4. High frequency sounds that cannot be heard by you are called …………
5. Pitch of a sound depends on the ………… vibration.
6. If the thickness of a vibrating string is increased, its pitch …………

Answer:

1. vibrating bodies
2. oscillation
3. mechanical waves
4. Ultrasonic
5. frequency of the
6. decrease

III. Match the following:

1. Ultrasonics                   – Frequency below 20Hz
2. Speed of sound in air – Needs material medium
3. Infrasonics                   – 330 m
4. Sound propagation     – Frequency more than 20000 Hz

Answer:

1. Ultrasonics – Frequency more than 20000 Hz
2. Speed of sound in air – 330 m
3. Infrasonics – Frequency below 20Hz
4. Sound propagation – Needs material medium

IV. Choose the correct option:

(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.
(e) Both Assertion and reason are false.

1. Assertion: When lightning strikes, the sound is heard a little after the flash is seen.
Reason: The velocity of light is greater than that of the sound.
Answer:
(a) Both assertion and reason are true and reason is the correct explanation of assertion.

2. Assertion: Two persons on the surface of moon cannot talk to each other.
Reason: There is no atmosphere on moon.
Answer:
(a) Both assertion and reason are true and reason is the correct explanation of assertion.

V. Answer briefly:

1. What are vibrations?
Answer:
Vibration means a kind of rapid to and fro motion of an object.

2. Give an example to show that light travels faster than sound.
Answer:
Lightning:
The most common example of showing that light travels faster than sound is lightning. Whenever a lightning strikes, you see the lightning first and then hear the thunder after some time.

3. To increase loudness of sound by four times, by how much should the amplitude of vibration be changed?
Answer:
Loudness of a sound depends on the amplitude of the vibration. So to increase loudness of sound by four times, the amplitude of the vibration also to be increased by four times.

4. What is an ultrasonic sound?
Answer:
A sound with a frequency greater than 20000 Hz is called as ultrasonic sound.

5. Give two differences between music and noise.
Answer:
Music:

1. The sound that provides a pleasing sensation to the ear.
2. It is produced by the regular patterns of vibrations.

Noise:

1. Sound that is unpleasant to the ear
2. It is produced by the irregular and non-periodic vibrations.

6. What are the hazards of noise pollution?
Answer:

1. Noise may cause irritation, stress, nervousness and headache.
2. Long term exposure to noise may change the sleeping pattern of a person.
3. Sustained exposure to noise may affect hearing ability. Sometimes, it leads to loss of hearing.
4. Sudden exposure to louder noise may cause a heart attack and unconsciousness.
5. Noise of horns, loud speakers, etc., cause disturbances leading to lack of concentration.
6. Noise pollution affects a person’s peace of mind.

7. Mention few measures to be taken to reduce the effect of noise pollution.
Answer:

1. Strict guidelines should be set for the use of loudspeakers on social, religious and political occasions.
2. All automobiles should have effective silencers.

8. Define the following terms:

1. Amplitude
2. Loudness

Answer:

Amplitude:
Amplitude is the maximum displacement of a vibrating particle from its mean position. It is denoted by ‘A’ and its unit is ‘metre’ (m).

Loudness:
It is defined as the characteristic of a sound that enables us to distinguish a weak or feeble sound from a loud sound. The unit of loudness of sound is decibel (dB).

9. How does planting trees help in reducing noise pollution?
Answer:

• Plant parts such as stems, leaves, branches wood, etc., absorb sound.
• Rough bark and thick, fleshy leaves are particularly effective at absorbing sound due to their dynamic surface area and helps in reducing noise pollution.

Other Important links for 8th Science Book Back Answers:

Click here for Samacheer Kalvi 8th Science Book Back Solutions – 8th Science Book Back Answers