Sound - Production of sound Q/A
1. Write answers to the following questions.
(a) Why do we hear musical notes when strings of a sitar are
plucked?
(b) How does a bat find its way in the dark?
(c) What is the SONAR system based on?
(d) Why is the sound of the bell smothered when a hand is
placed on it?
2. Fill in the blanks.
(a) Man can hear sounds of sound frequencies between 20 and ……………
Hz.
(b) Amplitude and …………….. are not related.
(c) The period of oscillation depends upon the ………………. Of the
pendulum.
3. Match the following
Group ‘A’ Group
‘B’
(a)
frequency 1.
ultrasonic sound
(b)
period of oscillation 2. metre
(c)
amplitude 3.
second
(d) bat 4.
hertz
5.
audible sound
4. True or false?
(a) Frequency increases if amplitude is increased.
(b) A bat uses the principle of radar system while flying at
night.
(c) Ultrasonic sounds are produced in the sonar system.
ANSWERS
1. Write answers to the following questions.
(a) Why do we hear musical notes when strings of a sitar
are plucked?
ANS: 1) Vibration
of source is necessary for the production of the sound.
2) When
we pluck the strings of a sitar, they vibrate and we hear characteristic
sound.
3) These
characteristics sounds are different musical notes.
4)
Therefore we hear musical notes when strings of a sitar are plucked.
(b) How does a bat find its way in the dark?
ANS: 1) The
bats produce ultrasonic sounds while flying in the dark.
2)
That sound is reflected from objects in front of the bat.
3)
From the reflected sound the bat comes to know of the position of things
in its surroundings.
4)
Thus it is said that, with the help of ultrasonic sound a bat ‘sees’ with
its ears to find its way in the dark.
(c) What is the SONAR system based on?
ANS: 1) Sonar
system is based on the ultrasonic sound.
2)
Sonar is a kind of radar system
3)
Ultrasonic sounds are produced and caused to be reflected.
4)
The radar system tells the position of the objects by getting the waves
it produces reflected from targets in front.
5)
Sonar system is used to detect impurities inside the metal, also to measure the
depth of the ocean floor etc
(d) Why is the sound of the bell smothered when a hand
is placed on it?
ANS: 1) Vibration
of source is necessary for the production of the sound.
2) The
sound of the bell is produced because vibrations of the bell.
3)
If we place our over the vibrating bell, the vibrations are interrupted.
4)
Therefore, the sound of the bell smothered when a hand is placed on it
2. Fill in the blanks.
(a) Man can hear sounds of sound frequencies between 20
and 20,000 Hz.
(b) Amplitude and frequency are not
related.
(c) The period of oscillation depends upon the length of the pendulum.
3. Match the following
Group
‘A’ Group
‘B’
(a)
frequency 4.
hertz
(b)
period of oscillation 3. second
(c)
amplitude 2.
metre
(d)
bat 1.
ultrasonic sound
4. True or false?
(a) Frequency increases if amplitude is increased.
Ans: False [Even if frequency is increased amplitude
remains the same]
(b) A bat uses the principle of radar system while
flying at night.
Ans: False [A bat uses ultrasonic sounds while flying
at the night]
(c) Ultrasonic sounds are produced in the sonar
system.
Ans: True
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