Practice exercise of class 8 science of Jawahar Navodaya Vidyalaya
1. Which one of the following statements is correct regarding the velocity of sound ?
a. It is maximum in gases and minimum in liquids
b. It is maximum in solids and minimum in gases
c. It is maximum in liquid and minimum in solids
d. It is maximum in solids and minimum in gases
answer d
2. The ceiling of a concert hall are generally curved because
a. they reflect the sound to the audience
b. they can absorb noise
c. it is better aeration in the hall
d. all of these
answer b
3. A human heart beats 72 times in a minute. Its frequency will be
a. 1.9 Hz
b. 1.2 Hz
c. 2.5 Hz
d. 8.2 Hz
answer b
4. If sound of lightening is heard after 12 seconds of lightening, then distance of observation of sound from the place where lightening occurs, is ( Given, speed is sound = 330/s)
a. 1980 m
b. 2970 m
c. 3960 m
d. 1485 m
answer c
5. Loudness of sound can be increased by
a. increasing frequency
b. decreasing frequency
c. increasing amplitude
d. decreasing amplitude
answer c
6. A sound wave has frequency of 2 kHz and wavelength of 35 cm. If an observer is 1.4 km away from the source. At what time interval could the observer hear the sound?
a. 2s
b. 20s
c. 0.5s
d. 4s
answer a
7. A person rings a metallic bell near a strong concrete wall. He hears the echo after 0.3s. If the sound moves with a speed of 340 m/s. The wall is far from him?
a. 102 m
b. 11 m
c. 51 m
d. 30 m
answer c
8. A baby recognizes her mother by her voice. The characteristics of sound involved is
a. quality
b. pitch
c. loudness
d. shrillness
answer a
9. By which property of sound the change in air temperature is affected?
a. Amplitude
b. Intensity
c. Frequency
d. Wavelength
answer d
10. Sound waves are similar to the waves
a. of laser light passing through air
b. generated in a stretched wire by hitting or plucking the wire
c. generated in a pipe filled with air by moving the piston attached to the pipe up and down
d. generated by the mobile phone tower
answer c
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