Sound

Samacheer Book Back Questions And Answers For Science Standard 8 “Sound“

I. Choose the best answer:
1. Sound waves travel very fast in
a. air
b. metals
c. vacuum
d. liquids

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

3. The amplitude of the sound wave decides its
a. speed
b. pitch
c. loudness
d. frequency

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

5. Find the odd one out.
a. Harmonium
b. Flute
c. Nadaswaram
d. Violin

6. Noise is produced by
a. vibrations with high frequency.
b. regular vibrations.
c. regular and periodic vibrations.
d. irregular and 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

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.

9. Which of the following may be caused by noise?
a. Irritation
b. Stress
c. Nervousness
d. All the above

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 _____ of the vibration.
6. If the thickness of a vibrating string is increased, its pitch _____.

Answers:
1. Vibrating bodies
2. Oscillation
3. Mechanical waves
4. Ultrasonic
5. Frequency
6. Decrease

III. Match the following:
1. Ultrasonics                      A. Frequency below 20Hz
2. Speed of sound in air     B. Needs material medium
3. Infrasonic                        C. 330ms^-1
4. Sound propagation        D. Frequency more than 20000 Hz

Answers:
1. D
2. C
3. A
4. B

IV. Consider the statements given below and choose the correct option:
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.
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.

2. Assertion: Two persons on the surface of moon cannot talk to each other.
Reason: There is no atmosphere on moon.
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.

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