Sound: Production of Sound
Maharashtra Board-Class 7th-General Science-Chapter-18
Solutions
Question 1:
Fill in the blanks .
(a) Sound is generated by the rhythmic ............. of an object.
(b) The frequency of sound is measured in ............... .
(c) If ............. of sound is decreased , its loudness also decreases.
(d) A medium is necessary for .................... of sound.
(a) Sound is generated by the rhythmic vibrations of an object. (b) The frequency of sound is measured in Hertz (Hz). (c) If amplitude of sound is decreased, its loudness also decreases. (d) A medium is necessary for propagation of sound.
Question 2:
Match the pairs
Group 'A' | Group 'B' |
(a) Flute | (1) Frequency less than 20 Hz |
(b) Frequency | (2) Frequency more than 20000 Hz |
(c) Sound level | (3) Vibrations in the air |
(d) Ultrasonic sound | (4) Measured in Hz |
(e) Infrasonic sound | (5) Decibel |
Group 'A'
Group 'B'
(a) Flute
Vibrations in the air
(b) Frequency
Measured in Hz
(c) Sound level
Decibel
(d) Ultrasonic sound
Frequency more than 20000 Hz
(e) Infrasonic sound
Frequency less than 20 Hz
Question 3:
Give scientific reasons. Thus, in earlier times, people used to listen for the arrival of a distant train by putting their ear to the rail.
(a) In earlier times, people used to listen for the arrival of a distant train by putting their ear to the rail.
(b) The sounds generated by a tabla and a sitar are different.
Thus, the sounds generated by a tabla and a sitar is different.
(c) If you were both on the moon , your friend will not be able to hear you call. We know that This is the reason, why your friend will not be able to hear your call.
(d) We can hear the movement of a mosquito's wings but we cannot hear the movement of our hands.
Thus, the movement of our hands cannot be heard.
Question 4:
Write answers to the following questions .
(a) How is sound produced ? Vibrations are produced in an object when it is struck. Vibrations are produced in an object when it is struck. Vibrating object is a source of sound. The rhythmic vibrations of an object produces sound.
(b) What does the intensity of sound depend upon ? The intensity of sound depends upon :
(c) Explain how the frequency of oscillation is related to the length of a pendulum and the amplitude of its oscillation.
(d) Explain the two ways by which the pitch of the sound generated by a stretched string can be changed.
Frequency or pitch of vibration of a stretched string can be changed by varying the Using these ways, the pitch of the sound generated by a stretched wire can be changed.
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