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Resonance: examples and uses - class-XI

Description: resonance: examples and uses
Number of Questions: 30
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Tags: oscillatory motion physics oscillations free, damped and forced oscillations option b: engineering physics
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In an open pipe, the pressure variation at the ends of the pipe is maximum.

  1. True

  2. False

  3. Nither

  4. Either


Correct Option: B
Explanation:

A suction at the end of the tube draws air from further up the tube, and that in turn draws air from further up the tube and so on. So the result is that a pulse of high pressure air travelling down the tube is reflected as a pulse of low pressure air traveling up the tube. So the pressure wave has been reflected at the open end, with a change in phase of 180. In the open-open pipe, there is such a reflection at both ends. So the above argument is false.

Two understand oscillators are known to have the same neutral frequency $ \omega _0 $ . The mass and damping coefficient of the first oscillator are $m _1 $ and $b _1 $ , and the mass and damping coefficient of the second oscillator are $m _2 $ and $b _2$ , respectively. A sinusoidal driving force of $F _{ext} = F _0 \cos \omega t $ is applied to each oscillator. Starting with $\omega $ far from $ \omega _0$ the driving force is tuned in order to observe resonant behavior. If $ m _1 = 4 m _2 $ and $b _1 = 2b _2 $ , then which one the following statements concerning the driven oscillations is correct?

  1. The resonant peak of the first driven oscillator is higher and narrower than that of the second oscillator.

  2. The resonant peak of the first driven oscillator is higher and wider than that of the second oscillator.

  3. The resonant peak of the first driven oscillator is lower and wider than that of the second oscillator.

  4. The resonant peak of the first driven oscillator is lower and narrower than that of the second oscillator.


Correct Option: A

A student is performing the experiment of resonance Column. The diameter of the column tube is $4\ cm$. The frequency of the tuning fork is $512\ Hz$. The air temperature $38^{o}C$ in which the speed sound is $336\ m/s$. The zero of the meter scale coincides with the top end of the Resonance Column tube. When the first resonance occurs, the reading of the water level in the column is:

  1. $14.0\ cm$

  2. $15.2\ cm$

  3. $16.4\ cm$

  4. $17.6\ cm$


Correct Option: B
Explanation:

For $I^{st}$ resonance

$l _1 + e = \dfrac{\lambda}{4}$ or $l _1 = \dfrac{\nu}{4f} - 0.3d = 15.2\space cm$

The example of forced vibration is

  1. resonance.

  2. beats.

  3. interference.

  4. diffraction.


Correct Option: A
Explanation:

when one object vibrating at the same natural frequency of a second object forcesis called resonance.

so that correct option is A.

Amplitude of a wave is represented by  $A=\frac{c}{a+b-c}$ Then resonance will occur when

  1. b = -c/2

  2. b = 0 and a = c

  3. b = - a/2

  4. None of these


Correct Option: B
Explanation:

$A=\dfrac{c}{a+b-c}$ : When  b = 0, a = c
Amplitude $A\rightarrow \infty$. This corresponds to resonance

If two vibrating systems are in resonance, then :

  1. Their amplitudes are equal

  2. Their frequencies are equal

  3. Their temperatures are equal

  4. Their intensities are equal


Correct Option: B
Explanation:

Answer is C.

Resonance is a phenomenon that consists of a given system being driven by another vibrating system or by external forces to oscillate with greater amplitude at some preferential frequencies. Frequencies at which the response amplitude is a relative maximum are known as the system's resonant frequencies, or resonance frequencies. 
When both the bodies vibrate, they will start to vibrate with the same frequency.

State whether the given statement is True or False :
One example of resonance involving visible and invisible light in the electromagnetic spectrum is resonance fluorescence. 

  1. True

  2. False


Correct Option: A
Explanation:

One example of resonance involving visible and invisible light in the electromagnetic spectrum is resonance fluorescence. Fluorescence itself is a process whereby a material absorbs electromagnetic radiation from one source, then re-emits that radiation on a wavelength longer than that of the illuminating radiation. 

Among its many applications are the fluorescent lights found in many homes and public buildings. Sometimes the emitted radiation has the same wavelength as the absorbed radiation, and this is called resonance fluorescence.
Resonance fluorescence is used in laboratories for analyzing phenomena such as the flow of gases in a wind tunnel.

Resonance is exhibited in 

  1. quartz crystals

  2. clocks

  3. ear membranes

  4. pendulum


Correct Option: A,B,C,D
Explanation:

$Answer:-$ A,B,C,D

Various examples of mechanical resonance include:

  • Most clocks keep time by mechanical resonance in a balance wheel,pendulum, or quartz crystal.
  • Orbital resonance as in some moons of the solar system's gas giants.
  • The resonance of the basilar membrane in the ear.
  • Making a child's swing swing higher by pushing it at each swing.
  • A wineglass breaking when someone sings a loud note at exactly the right pitch.

What conditions are necessary to produce resonance in an object?

  1. The object must have at least one natural frequency of vibration.

  2. The object must be driven by an external vibrating force.

  3. The frequency of the external vibrating force must match the object's natural frequency of vibration.

  4. All of the above.


Correct Option: D
Explanation:

Resonance is a phenomenon in which the periodic oscillatory force acting on an object has a frequency of vibration same as the natural frequency of the object. In this, the object vibrates with a large amplitude.

Pick the wrong statement:

Interference to occur:

  1. frequency of one wave should be equal to another

  2. amplitude of one wave should be comparable to that of another

  3. one wave must superpose on another

  4. frequency of two waves can never be same / equal


Correct Option: D
Explanation:

Interference is a phenomenon in which two waves of equal frequencies and nearly equal amplitudes superpose on one another and produce a resultant new wave.

If a singer could match the natural frequency of the wine glass, he:

  1. can shatter the glass

  2. can still never shatter the glass

  3. can at most vibrate the glass

  4. can leave no effect on the glass


Correct Option: A
Explanation:

$Answer:-$ A 

If a singer could match the natural frequency of the wine glass than he could possibly shatter the glass as coming into resonance would make every atomic particle of glass to vibrate and thereby increasing distance between two particles and hence can actually break.

State whether the given statement is True or False :

Resonance is the cause of sound production in musical instruments.

  1. True

  2. False


Correct Option: A
Explanation:

Resonance is cause of sound production in musical in instrument. this statement is true. Generally musical instrument have a hollow chamber, it contains air particle. when vibration is produced, it may be in the objects attached to it, the frequency of this object may match with a natural frequency of air particle inside the hollow chamber. Thus the air particles start to vibrate with the large amplitude which produces large sound. 

Resonance occurs when a vibrating system or external force drives another system to ____ with greater _ at a specific preferential ______. Fill in the blanks. 

  1. oscillate, amplitude, frequency

  2. oscillate, frequency, amplitude

  3. vibrate, velocity, frequency

  4. vibrate, frequency, velocity


Correct Option: A
Explanation:

$Answer:-$ A

In physics, resonance is a phenomenon that occurs when a given system is driven by another vibrating system or external force to oscillate with greater amplitude at a specific preferential frequency.

Resonance occurs when a system is able to store and easily transfer energy between two or more different storage modes (such as kinetic energy and potential energy in the case of a pendulum). However, there are some losses from cycle to cycle, called damping. When damping is small, the resonant frequency is approximately equal to the natural frequencyof the system, which is a frequency of unforced vibrations. Some systems have multiple, distinct, resonant frequencies.
Resonance phenomena occur with all types of vibrations or waves: there is mechanical resonanceacoustic resonanceelectromagnetic resonance, nuclear magnetic resonance(NMR), electron spin resonance (ESR) and resonance of quantum wave functions. Resonant systems can be used to generate vibrations of a specific frequency (e.g., musical instruments), or pick out specific frequencies from a complex vibration containing many frequencies (e.g., filters).

In a resonance tube with tuning fork of frequency $512 \ Hz$, first resonance occurs at water level equal to $30.3 \ cm$ and second resonance occurs at $63.7 \ cm$. The maximum possible error in the speed of sound is

  1. $51.2 \ cm/s$

  2. $102.4 \ cm/s$

  3. $204.8 \ cm/s$

  4. $153.6 \ cm/s$


Correct Option: C
Explanation:

$\begin{array}{l} { l _{ 1 } }+e=\frac { V }{ { 4f } } \to \left( i \right)  \ { l _{ 2 } }+e=\frac { { 3V } }{ { 4f } } \to \left( { ii } \right)  \ Sub\, \, \left( { ii } \right) \, \, & \, \, \left( i \right)  \ { l _{ 2 } }-{ l _{ 1 } }=\frac { { 2V } }{ { 4f } }  \ { l _{ 2 } }-{ l _{ 1 } }=\frac { V }{ { 2f } }  \ \frac { { \Delta \left( { { l _{ 2 } }-{ l _{ 1 } } } \right)  } }{ { { l _{ 2 } }-{ l _{ 1 } } } } =\frac { { \Delta V } }{ V }  \ \Delta V=2f\Delta \left( { { l _{ 2 } }-{ l _{ 1 } } } \right) =2f\left( { \Delta { l _{ 1 } }+\Delta { l _{ 2 } } } \right) ......for\, \, man\, \, error \ =2\times 512\times \left( { 0.1+0.1 } \right) =204.8\, \, cm/s \end{array}$

The phenomenon of resonance is used in receiving the radio and television programmes.

  1. True

  2. False

  3. Nither

  4. Either


Correct Option: A
Explanation:

This is a resonance in the circuit--- when you have a bunch of different

frequencies driving a resonant system, the response is only strong for

those frequencies which are close to the natural frequency of the

resonant oscillator. The frequency dependent amplification  is used to done through the resonance circuit for a desired frequency.

In a resonance column experiment the first resonance is obtained when the level of the water in tube is $20$cm from the open end. Resonance will also be obtained when the water level is at a distance of :

  1. $40$ cm from the open end

  2. $60$ cm from the open end

  3. $80$ cm from the open end

  4. $100$ cm from the open end


Correct Option: B,D
Explanation:
For $1^{st}$ resonance $(1/4)\lambda =L$
$\Rightarrow \lambda =4L$ ..(i)
For $2$nd resonance
$3\left(\dfrac{\lambda}{4}\right)=L _2\Rightarrow \lambda =\dfrac{4L _2}{3}$ .(ii)
By using (i) and (ii)
$\dfrac{4L _2}{3}=4L _1$
$\Rightarrow L _2=3L _1=3(20)=60$cm
Similarly, $L _3=5L _1=100$ cm
Hence (B) and (D) are correct.

The third overtone of a pipe is found to be in unison with the first overtone of an open pipe. The ratio of lengths of the pipes is 

  1. $\dfrac { 3 }{ 4 }$

  2. $\dfrac { 3 }{ 5 }$

  3. $\dfrac { 2 }{ 5 }$

  4. $\dfrac { 7 }{ 4 }$


Correct Option: D

In case of a forced vibration, the resonance wave becomes very sharp when the

  1. restoring force is small

  2. applied force is small

  3. damping is small

  4. quality factor is small


Correct Option: C
Explanation:

at resonance,the damping force becomes small enough so that the resulting oscillations have large amplitude.

In Resonance tube experiment, if $400\ Hz$ tuning fork is used, the first resonance occurs when length of air column in the tube is $19\ cm$. If the $400\ Hz$. tuning fork is replaced by $1600\ Hz$ tuning fork then to get resonance, the water level in the tube should be further lowered by (take end correction $= 1\ cm)$.

  1. $5\ cm$

  2. $10\ cm$

  3. $25\ cm$

  4. $20\ cm$


Correct Option: A

The first resonance length of a resonance tube is 40 cm and the second resonance length is 122 cm.third resonance length of the tube will be

  1. 200 cm

  2. 202 cm

  3. 203 cm

  4. 204 cm


Correct Option: C
Explanation:

The first resonant is$:-$

${L _1} = \frac{\lambda }{4}$
The second resonant length is$:-$
${L _2} = \frac{{3\lambda }}{4}$
the third resonant length of resonance tube is$:-$
${L _5} = 5\,\,\frac{\lambda }{4} = \frac{5}{3}\,\,{L _3} = \frac{5}{3}\left( {122\,cm} \right)$
Hence,
option $(C)$ is correct answer.

A organ pipe open on both ends in the $n^{th}$ harmonic is in resonance with a source of $1000 \,Hz$. The length of pipe is $16.6 \,cm$ and speed of sound in air is $332 \,m/sec$. Find the value of $n$.

  1. $1$

  2. $2$

  3. $3$

  4. $4$


Correct Option: A
Explanation:

$f = \dfrac{nV}{2\ell}$

$1000 = \dfrac{n \times 332}{2 \times 16.6 \times 10^{-2}}$

$10 = \dfrac{n \times 332}{33.2}$

$n = 1$

In a forced harmonic oscillator of natural frequency $\omega _0$, the resonant frequency $\omega _r$ is

  1. $>\omega _0$

  2. $<\omega _0$

  3. $=\omega _0$

  4. not related to $\omega _0$


Correct Option: C
Explanation:

The resonant frequency is always equal to natural frequency, hence option C is correct.

Resonance is a special case of $\underline{           }$ vibrations, when frequency of the driving force is$\underline{           }$ natural frequency of the body.

  1. forced, equal to the

  2. particle , more then the

  3. wave, equal to the

  4. forced, less than the


Correct Option: A
Explanation:

Resonance is a special case of forced vibrations, when frequency of the driving force is equal to the natural frequency of the body.
Resonance is the result of an external force vibrating at the same frequency as the natural frequency of a system. Natural frequency is a characteristic of every machine, structure and even animals. Often, resonance can be confused with the natural frequency or critical frequency. If equipment is operating in a state of resonance, the vibration levels will be amplified significantly, which can cause equipment failure and plant downtime. It is, therefore, important that the running speed of equipment be out of the resonance range.

A forced oscillator is acted upon by a force $F={ F } _{ \circ  }sin\omega t.$. The amplitude of oscillation is given by $\displaystyle\frac{55}{\sqrt{2\omega^2 - 36\omega + 9}}$. The resonant angular frequency is

  1. $2\space unit$

  2. $9\space unit$

  3. $18\space unit$

  4. $36\space unit$


Correct Option: B
Explanation:

At resonance, amplitude of oscillation is maximum
$\quad \Rightarrow 2\omega^2 - 36\omega + 9$ is maximum
$\quad \Rightarrow 4\omega - 36 = 0$ (derivative is zero)
$\quad \Rightarrow \omega = 9$

Imagine a child sitting on a swing in a park and the child's mother is pushing the swing from the back. The mother maintains the same tempo as the motion of the swing. If the mother tries to push at a faster tempo, the arc of the swing will:

  1. increase

  2. decrease

  3. remain the same

  4. become zero, i.e., the swing will stop


Correct Option: B
Explanation:

As the mother maintains the same tempo as the motion of the swing, it means frequency of mother and the swing is same, there is resonance. When mother tries to push at a faster tempo, frequency of mother changes and resonance is disturbed due to which, the arc of swing (amplitude) decreases.

A vibrating object will pick out its __________ from a complex excitation and vibrate at those frequencies.

  1. resonant frequency

  2. natural frequency

  3. both

  4. none


Correct Option: A
Explanation:

A vibrating object will pick out its resonant frequencies from a complex excitation and vibrate at those frequencies, essentially "filtering out" other frequencies present in the excitation.

State whether the given statement is True or False :
By tuning ultra sound waves to the natural frequency of a kidney stone, we can rely on resonance to pulverize the stone.

  1. True

  2. False


Correct Option: A
Explanation:

By turning ultrasound waves to the natural frequency of a kidney stone, we rely on resonance to parcels which the stones consist of vibrate with large amplitude and at a certain moment, this vibration causes breakdown of stone into pieces. So the given statement is true.

Which one does not work on principles of resonance?

  1. T.V

  2. Radio

  3. Microwave oven

  4. Bulb


Correct Option: D
Explanation:

Resonance in an electrical circuit is a phenomenon in which the inductive reactance and the capacitive reactance become equal and cancel each other.

As a result, the impedance of the circuit becomes the least and maximum current flows through the circuit. This happens only at a particular frequency of the AC power supply, known as resonant frequency. 
All the devices except bulb work on this principle. The circuit in them is tuned in order to make their resonant frequency matching with the desired one. This is done by adjusting the values of the inductor or the capacitor.
In a bulb, there is only pure resistance and no reactive component. There is no question of resonance.

In a resonance column experiment, the first resonance is obtained when the level of the water in tube is $20 cm$ from the open end. Resonance will also be obtained when the water level is at a distance of

  1. $40 cm$ from the open end.

  2. $60 cm$ from the open end.

  3. $80 cm$ from the open end.

  4. data insufficient.


Correct Option: B
Explanation:

In a closed pipe : length of the pipe is length of the air column in fundamental.

$\dfrac { \lambda  }{ 4 } =20cm$ 
${ 2 }^{ nd }$ harmonic resonance $=\dfrac { 3\lambda  }{ 4 } =3\times 20=60cm$

$\therefore $  Option (B) is correct.

Assertion : In the ideal case of zero damping, the amplitude of simple harmonic motion at resonance is infinite.
Reason : All real systems have some damping.

  1. If both assertion and reason are true and reason is the correct explanation of assertion.

  2. If both assertion and reason are true and reason is not the correct explanation of assertion.

  3. If assertion is true but reason is false.

  4. If both assertion and reason are false.


Correct Option: B
Explanation:

If there was no damping in the swing, the swing would move with larger and larger amplitudes. However, most physical systems have damping, which limits the size of the amplitude. If you don not have damping the amplitudes will go to infinity.

So, Assertion and reason both are true. But reason is not current explanation for the assertion.

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