Tag: physics

Questions Related to physics

Which of the following is the longitudinal wave?

physics study of sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

  1. Sound waves

  2. Waves on plucked string

  3. Water waves

  4. Light waves

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Correct Option: A
Explanation:

In sound waves vibration of particle is along the propagation of wave So it is longitudinal and in other options all are transverse wave as vibration of particle is perpendicular to the propagation of wave.  

Consider the following statement:
(a) Sound waves are longitudinal in nature.
(b) Sound waves cannot travel through vacuum.
(c) Sound waves are produced by oscillating charged particles only.
(d) Sound waves are electromagnetic waves.
Which of the following statements are correct ?

physics study of sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

  1. (a) and (b)

  2. (b) and (c)

  3. (a), (b) and (d)

  4. (a),(b),(c) and (d)

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Correct Option: A
Explanation:

Sound waves are longitudinal waves. It needs a medium to propagate. Sound waves are example of mechanical waves, not electromagnetic waves. Electromagnetic waves are created by the vibration of an electric charge.

A longitudinal waves consists of

physics study of sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

  1. crest and troughs in the medium

  2. compressions and rarefactions in the medium

  3. crest and troughs in vacuum 

  4. Both A and B

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Correct Option: B
Explanation:

Longitudinal waves, also known as l-waves, are waves in which the displacement of the medium is in the same direction as, or the opposite direction to, the direction of travel of the wave. Longitudinal waves are also called compression waves or compression waves, because they produce compression and rarefaction when traveling through a medium.  In longitudinal waves, the displacement of the particle's is parallel to the propagation of the wave. 

In case of longitudinal waves, the particles of medium vibrate

physics study of sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

  1. in the direction of wave propagation

  2. opposite to the direction of wave propagation

  3. at right angles to the direction of wave propagation

  4. none of the above

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Correct Option: A
Explanation:

Longitudinal waves, also known as l-waves, are waves in which the displacement of the medium is in the same direction as the direction of travel of the wave. Longitudinal waves are also called compressional waves or compression waves, because they produce compression and rarefaction when traveling through a medium.

Longitudinal waves are also called

physics study of sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

  1. Rarefactional waves

  2. Compressional waves

  3. Sound waves

  4. Light waves

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Correct Option: B
Explanation:

Sound is a mechanical wave that results from the back and forth vibration of the particles of the medium through which the sound wave is moving. If a sound wave is moving from left to right through air, then particles of air will be displaced both rightward and leftward as the energy of the sound wave passes through it. The motion of the particles is parallel to the direction of the energy transport. This is what characterizes sound waves in air as longitudinal waves.
Longitudinal waves, also known as l-waves, are waves in which the displacement of the medium is in the same direction as, or the opposite direction to, the direction of travel of the wave. Longitudinal waves are also called compressional waves or compression waves, because they produce compression and rarefaction when traveling through a medium.  In longitudinal waves, the displacement of the medium is parallel to the propagation of the wave.

769Hz longitudinal wave in air has a speed of 344m/s. How much time is required for the phase to change by 90 degrees at a given point in space? 

physics sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

  1. 0.325 ms

  2. 3.25 ms

  3. 32.5 ms

  4. 325 ms

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Correct Option: A
Explanation:

Given that, 

The frequency of wave is $\nu = 769 Hz$.

The speed of wave is $v = 344 ms^{-1}$.

We know, the frequency of a wave is the number of oscillations per 
unit time. The period (T) of a wave is the time that it takes for one complete oscillation, i.e., to change its phase through $360^\circ$.
Hence,

$T = \dfrac{1}{\nu}$

$T = \dfrac{1}{769}$

$T = 0.0013 s$

$T = 1.3 ms$
Here, the phase change is 90 degrees at a given point in space.  

$\dfrac{90}{360} = \dfrac{1}{4}$

Hence, the time period required to complete one fourth oscillation is

$T = \dfrac{1.3}{4} = 0.325 ms$

The musical note A is a sound wave. The note has a frequency of 440 Hz and a wavelength of 0.784 m. Calculate the speed of the musical note in m/s.

physics sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

  1. 343

  2. 345

  3. 34

  4. 346

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Correct Option: B
Explanation:

Let,

The frequency of the musical note is $\nu = 440 Hz = 440 s^{-1}$

The wavelength of the musical note is $\lambda = 0.784 m $

Now, the frequency of the musical note is 
$\nu = \dfrac{v}{\lambda}$

where, v is the speed of the musical note 
Hence, the speed of the musical note is
$v = \nu \lambda$

$v = 440 \times 0.784$

$v = 344.96 \approx 345 ms^{-1}$

The type of waves that can be propagated in solids are :

physics sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

  1. Longitudinal

  2. Transverse

  3. both

  4. None

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Correct Option: C
Explanation:

Mechanical waves (longitudinal waves and transverse waves) are waves which propagate through a material medium (solid, liquid or gas) at a wave speed which depends on the elastic and inertial properties of that medium. 
The transverse waves depends on the rigidity of the medium hence, can propagate through solid and liquid medium but not through gases.
The longitudinal waves depends on resistance to compression or volume elasticity of the medium hence, can propagate through solid, liquid and gases.

The frequency of a tuning fork is 384 Hz and velocity of sound in air is $\displaystyle 352 ms^{-1}$. How far sound has travelled when fork completes 36 vibration?

physics vibrations of stretched strings sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

  1. 33 m

  2. 16.5 m

  3. 11 m

  4. 22 m

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Correct Option: A
Explanation:

$\displaystyle x = v.t = v \times \dfrac{no \ of \ complete \ vibration }{frequency \ of fork}=325$ x $\displaystyle\frac{36}{384} = 33 m$

What is the ratio of the speed of sound in neon and water vapor at the same temperature. It is nearest to :

physics propagation of sound waves sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

  1. 2.5

  2. 2

  3. 1.5

  4. 1

Show answer
Correct Option: D
Explanation:

According to the Avogadro's law , at same temperature and pressure the number of molecules of different gasses are equal. Therefore density will not change in either case of neon or water vapor. And the speed of sound waves is a function of density and temperature. So in this case doesn't matter.
Option "D" is correct.