Tag: physics

Questions Related to physics

Sound waves of wavelength $\lambda $ travelling with velocity $v$ in a medium enter into another medium in which their velocity is $4v$. The wavelength in $2^{nd}$ medium is :

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

  1. $4\lambda$

  2. $\lambda $

  3. $\lambda/4 $

  4. $ 16\lambda $

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Correct Option: A
Explanation:

From $v=n\lambda $ we find $\lambda\propto v$ because frequency n is constant .

Therefore ,
new wavelength = $4\lambda $

A $40\ cm$ long brass rod is dropped, one end first on to a hard floor but it is caught before it topples over. With an oscilloscope it is determined that the impact produces a $3\ kHz$ tone. The speed of sound in brass is:

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

  1. $1200\ m/s$

  2. $2400\ m/s$

  3. $3600\ m/s$

  4. $3000\ m/s$

Show answer
Correct Option: B
Explanation:

Both ends are free and therefore antinodes are formed.
The relation between the wavelength of the wave and the length of the rod for fundamental frequency will be:

$\Rightarrow l=\dfrac{\lambda}{2} \ \ \Rightarrow \lambda=2l$

The speed of the wave in the rod is:
$v=f\lambda = 2\times 40\times 3\times 10^{3}$$=2400\ ms^{-1}$

The frequency of a man's voice is 300 Hz and its wavelength is 1 meter. If the wavelength of a child's voice is 1.5 m, then the frequency of the child's voice is :

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

  1. 200 Hz

  2. 150 Hz

  3. 100 Hz

  4. 350 Hz.

Show answer
Correct Option: A
Explanation:

$\nu _1\lambda _1= \nu _1\lambda _1$ since $v= \nu\lambda$ is same for both a man and child.

$ \therefore 300 \times 1 =  \nu _2 \times  1.5$


$ \Rightarrow \nu _2 = 200 : Hz$

The wave produced in a resonance tube is

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

  1. Longitudinal

  2. Transverse

  3. Transverse stationary

  4. Longitudinal stationary

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Correct Option: D
Explanation:

Waves produced in a resonance tube are sound waves. Two sound waves in opposite direction interfere with each other to create resonance. As sound waves are longitudinal waves, waves produced are longitudinal stationary. 

Two sound waves of wavelengths $1\space m$ and $1.01\space m$ produce $10$ beats in $3$ seconds. Then, the velocity of the sound is

physics superposition of waves-1: interference and beats sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

  1. $330\space ms^{-1}$

  2. $333.3\space ms^{-1}$

  3. $336.7\space ms^{-1}$

  4. none of the above

Show answer
Correct Option: C
Explanation:

From the formula, $v=f \lambda$

and the velocity of the sound in air is frequency independent.

for two frequencies $f _1$ and $f _2$, wavelengths are $\lambda _1$ 

and $\lambda _2$ , then the beats will be

$f _1-f _2=v\left(\dfrac{1}{\lambda _1}-\dfrac{1}{\lambda _2}\right)=v\left(\dfrac{\lambda _2-\lambda _1}{\lambda _2  \lambda _1}\right)$

$\dfrac{10}{3}=v\left(\dfrac{0.01}{1.0\times 1.01}\right)$

$v=\dfrac{10\times 1.0\times 1.01}{3.0\times 0.01}=336.66\ \text{ms}^{-1}$

Option "C" is correct.

Sound waves cannot pass through

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

  1. a solid-liquid mixture

  2. an ideal gas

  3. a liquid-gas mixture

  4. a pefect vacuum

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Correct Option: D
Explanation:

Sound cannot travel through a perfect vacuum. A vacuum is an area without any air, like space. So sound cannot travel through space because there is no matter for the vibration to work in.

Sound waves in air are _________ waves.

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

  1. longitudinal

  2. radio

  3. transverse

  4. electromagnetic

Show answer
Correct Option: A
Explanation:

Sound waves in air and any fluid medium are longitudinal waves because particles of the medium through which the sound is transported vibrate parallel to the direction that the sound waves moves.

A _________________ wave has oscillations in the same direction as its motion.

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

  1. Longitudinal

  2. Oscillatory

  3. Vibrational

  4. matter

Show answer
Correct Option: A
Explanation:

A longitudinal wave has oscillations in the same direction as its motion.
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.  In longitudinal waves, the displacement of the medium is parallel to the propagation of the wave. 

The sound propagates in a gaseous medium as :

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

  1. transverse waves

  2. longitudinal waves

  3. both (a) and (b)

  4. neither (a) nor (b)

Show answer
Correct Option: B
Explanation:

Sound is a sequence of waves of pressure which propagates through compressible media such as air or water. Sound propagates as longitudinal waves in gaseous medium. Longitudinal waves are the waves in which the displacement of the medium is in the same direction, or the opposite direction to the direction to the direction of propagation of wave.

Match the columns

i) particles of medium move parallel to the propagation of disturbance. a) Transverse wars
ii) particles of medium oscillate up and down about their mean position. b) longitudual wars.
iii) particles of the medium oscillate oscillate back and forth about their position of vest.
iv) particles move about their mean positions in a direction perpendicular to the direction of waves propagation
physics study of sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

  1. a - i, ii, b - iii, iv

  2. a - i, iii, b - ii, iv

  3. a - iii, iv, b - i, ii

  4. a - iv, ii, b - i, iii

Show answer
Correct Option: D
Explanation:

In a wave if the particles of medium , vibrate perpendicular to the direction of wave motion (disturbance) then this wave is called a longitudinal wave .

 If the particles of medium , vibrate parallel to the direction of wave motion (disturbance) then this wave is called a transverse wave .
According to these definitions , we can match the given columns as :
a-iv ,ii and b-i,iii .