Tag: time period, frequency and amplitude of sound

Questions Related to time period, frequency and amplitude of sound

Sound is produced by a

  1. vibrating body

  2. moving body

  3. oscillating body

  4. both A and C


Correct Option: A,B,C
Explanation:

Sound is produced by a vibrating body.
Sound is produced when something vibrates. The vibrating body causes the medium (water, air, etc.) around it to vibrate. Vibrations in air are called travelling longitudinal waves, which we can hear. Sound waves consist of areas of high and low pressure called compressions and rarefactions, respectively.

If one puts one ears to the steel rail, the sound of a coming train can be heard even when the train cannot be seen. One can conclude from this observation that
A. Sound travels faster in steel than in air.
B. Amplitude of sound in the rail is much larger than in air.
C. Sound can travel larger distance in solids than in air.
D. Quality of sound in rail is better than in air.
The reasonable conclusion are

  1. A and C

  2. A and B

  3. B and C

  4. None of these


Correct Option: B
Explanation:

Velocity of sound is maximum in solids and least in gases
$ V _{gas} < V _{liquid} < V _{solid} $
Intensity would also be much lower in air as $I \propto a^{2}$

How is the frequency of a wave related to its time period?

  1. $\ v=\displaystyle\frac{1}{T}$

  2. $\ T=\displaystyle\frac{1}{v}$

  3. $\ v T=\displaystyle{1}$

  4. All the above


Correct Option: D
Explanation:

Frequency is the number of occurrences of a repeating event per unit time. The Time period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency.

That is, $T=\dfrac { 1 }{ f } \quad \quad or\quad \quad f=\dfrac { 1 }{ T } $

Longitudinal waves are possible in 

  1. solids

  2. liquids

  3. gases

  4. All of these


Correct Option: D
Explanation:

For propagation of sound wave, medium is necessarry it might be in any form. Like solid liquid or gas.

The voices of Men, Women and children differ because of difference in their

  1. Lungs

  2. Wind pipr

  3. Vocal chords

  4. Larynx


Correct Option: C
Explanation:

Lungs are used to filter the oxygen from air .

Wind pipe provides a path for air to go inside the lungs .
Larynx is responsible for the production of sound .
Vocal cords are inside the larynx , and their thickness decides the frequency of sound (shrill or grave ) , by which we can differentiate between the voices of a man (grave) , women and children(shrill) .

When longitudinal wave propagates through a medium, then the physical quantities propagating in the direction of wave are

  1. Energy

  2. Energy, momentum and mass

  3. Energy and mass

  4. Energy and momentum


Correct Option: A
Explanation:

When a disturbance is produced in a medium , it is transported by oscillating particles of the medium , the disturbance is a kind of energy and carried by oscillating particles by passing it to the next particle , in this way a longitudinal wave propagates, therefore energy propagates in a longitudinal wave .

As there is no net movement of the medium particles in the propagation of wave , they just vibrate about the centers of rarefaction and compressions , therefore momentum is not transferred in a longitudinal wave . Thus only energy is propagating in the direction of wave. 

If the velocity of sound in a gas is $200 {ms}^{-1}$ when the temperature is $127^0  C$, then the velocity of sound in the same gas when temperature is increased by $900^0  F$ is ______ ${ms}^{-1}$

  1. $200\sqrt{3}$

  2. 300

  3. $100\sqrt{5}$

  4. 450


Correct Option: B

A sound wave is a pressure wave; regions of high (compressions) and low pressure (rarefactions) are established as the result of the vibrations of the sound source. These compressions and rarefactions result because sound :

  1. is more dense than air and thus has more inertia, causing the bunching up of sound

  2. waves have a speed which is dependent only upon the properties of the medium

  3. is like all waves; it is able to bend into the regions of space behind obstacles

  4. is able to reflect off fixed ends and interfere with incident waves vibrates longitudinally; the longitudinal movement of air produces pressure fluctuations


Correct Option: D
Explanation:

These compressions and rarefactions result because sound is able to reflect off fixed ends and interfere with incident waves vibrates longitudinally; the longitudinal movement of air produces pressure fluctuations. Compressions are the regions of high density and rarefactions are regions of low density.

The speed of highly penetrating ultrasonic waves is :

  1. Lower than those of audible sound waves

  2. Higher than those of audible sound wave

  3. Much higher than those of audible sound waves

  4. Same as those of audible sound waves


Correct Option: B
Explanation:

Speed of highly penetrating ultrasonic waves is greater than 20,000Hz equal to $10^7$Hz

Suppose a stick is struck against a frying pan in vacuum. Which of the following is/are true?

  1. the frying pan vibrate

  2. we be able to hear the sound

  3. we can hear the sound just for few minutes 

  4. None of the above


Correct Option: A
Explanation:

Sounds are made by vibrations. Some vibrations are easy to see.
In this case, a stick is struck against a frying pan in vacuum. The frying pan vibrates. But this happens in vacuum. Sound waves require a medium to travel through. Outer space is a vacuum, and therefore it is not heard.
Hence, the sound created by the stick and frying pan is not heard.