the correct answer.
Sound can travel through
(a) gases only
(b) solids only
(c) liquids only
(d) solids, liquids and gases.
Which of the following voices is likely to
have minimum frequency?
(a) Baby girl
(b) Baby boy
(c) A man
(d) A woman
the following statements, tick 'T' against those which are true, and 'F'
against those which are false.
cannot travel in vacuum. (T / F)
(b) The number of oscillations per second of a vibrating object is
called its time period. (T / F)
(c) If the amplitude of vibration is large, sound is feeble. (T /
(d) For human ears, the audible range is 20 Hz to 20,000 Hz. (T /
(e) The lower the frequency of vibration, the higher is the pitch.
(T / F)
(f) Unwanted or unpleasant sound is termed as
music. (T / F)
(g) Noise pollution may cause partial hearing
in the blanks with suitable words.
(a) Time taken
by an object to complete one oscillation is called _________.
is determined by the________ of vibration.
(c) The unit
of frequency is _________.
sound is called _________.
of a sound is determined by the _________of vibration.
(a) Time taken by an object to complete one
oscillation is called time period.
Loudness is determined by the amplitude of vibration.
unit of frequency is hertz (Hz).
Unwanted sound is called noise.
Shrillness of a sound is determined by the frequency of
A pendulum oscillates 40
times in 4 seconds. Find its time period and frequency.
Frequency of oscillation
is the number of oscillations of a vibrating object per second.
Therefore, here the frequency
is 40 vibrations /4 seconds = 10 Hertz.
Time period is the time required to
complete one oscillation. Therefore, it is the inverse of the time period.
Therefore, here the time period = 1/10 = 0.1 second.
The sound from a mosquito is
produced when it vibrates its wings at an average rate of 500 vibrations per
second. What is the time period of the vibration?
Time period is the
inverse of the frequency.
= 1/Frequency of oscillation = 1/500 = 0.002 sec.
Identify the part which vibrates to produce
sound in the following instruments.
(a) Diaphragm (stretched membrane)
(c) Air column
What is the difference
between noise and music? Can music become noise sometimes?
Noise is unwanted sound
that is unpleasant to the human ear, whereas music is a pleasant sound.
become noise. When someone tries to enjoy very loud music, it can become noise
for someone else. When loud music is played during celebrations, it can be
annoying for many people.
List sources of noise
pollution in your surroundings.
Some sources of noise
pollution are as follows:
Televisions played at high volumes and sound of
Bursting of crackers and blaring sound from
Honking horns of vehicles.
Home appliances such as mixers, desert coolers,
Explain in what way noise
pollution is harmful to humans.
Noise pollution is
harmful to humans and can lead to a number of health issues. Some examples are
Loss of hearing
Your parents are going to buy
a house. They have been offered one on the roadside and another three lanes
away from the roadside. Which house would you suggest your parents should buy?
Explain your answer.
A house by the roadside
will have more noise pollution produced from transportation vehicles plying on
the road. On the other hand, a house which is three lanes away from the
roadside would be quieter. Therefore, I would suggest to take the house that is
away from the roadside.
Sketch larynx and explain its
function in your own words.
Larynx is a part of the
throat and it is responsible for production of sound.
Lightning and thunder take
place in the sky at the same time and at the same distance from us. Lightning
is seen earlier and thunder is heard later. Can you explain?
During lightning, we see
the streak of light earlier than hearing the sound of thunder because the speed
of light is greater than the speed of sound. Owing to this, the light from
a lightning reaches us faster than the sound of thunder.