Physics

Wave Motion

489 Questions

Wave motion questions cover the principles of traveling and stationary waves, including their equations and intensities. The topics explore interference patterns, phase differences, and electromagnetic radiation speeds. Mastery of these concepts is vital for physics sections in engineering and civil services examinations.

Wave interferenceStanding wavesPhase differenceElectromagnetic radiationWave equations

Wave Motion Questions

Multiple choice luminous intensity measurements physics

Two coherent source must have the same :

  1. amplitude

  2. phase difference

  3. frequency

  4. both B and C
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Two coherent source have the same :

1) Frequency
2) Phase difference.

The correct option is D.

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

 769Hz longitudinal wave in air has a speed of 344m/s. At a particular instant, what is the phase difference (in degrees) between two points 5.0 cm apart?

  1. 30

  2. 40

  3. 45

  4. 60
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Given that,

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

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

The wavelength of wave is given by

$\lambda = \dfrac{v}{\nu}$

$\lambda = \dfrac{344}{769}$

$\lambda = 0.447 m = 44.7 cm$

Hence, the phase difference between two points 5.0 cm apart is

$\dfrac{5}{44.7} \times 360^\circ = 0.1118 \times 360^\circ = 40.24^\circ \approx40^\circ$

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

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 :

  1. $4\lambda$
  2. $\lambda $
  3. $\lambda/4 $
  4. $ 16\lambda $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

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

Therefore ,
new wavelength = $4\lambda $

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

The wave produced in a resonance tube is

  1. Longitudinal

  2. Transverse

  3. Transverse stationary

  4. Longitudinal stationary
Reveal answer Fill a bubble to check yourself
D Correct answer
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. 

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

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

  1. Longitudinal

  2. Oscillatory

  3. Vibrational

  4. matter
Reveal answer Fill a bubble to check yourself
A Correct answer
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. 

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

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

  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
Reveal answer Fill a bubble to check yourself
D Correct answer
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 . 

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

The waves in which the particles of the medium vibrate in a direction perpendicular to the direction of wave motion is known as:

  1. transverse wave

  2. propagated waves

  3. longitudinal waves

  4. stationary waves
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The waves in which the particles of the medium vibrate in a direction perpendicular to the direction of wave motion is known as transverse wave. Examples of these waves are: vibrations in strings, ripples on water surface and electromagnetic waves.

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

How longitudinal waves are different from other waves?

  1. Particles of medium move in a direction parallel to direction of energy transport

  2. Particles of medium move in a direction perpendicular to direction of energy transport

  3. Particles of medium move in a direction below to direction of energy transport

  4. None
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Longitudinal waves are different from the others waves because in longitudinal waves particles of medium move in a direction parallel to direction of energy transport for longitudinal waves.

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

In a graphical presentation of longitudinal waves as attached, the peak of wave is called

  1. Compression

  2. Rarefaction

  3. Reflection

  4. Refraction
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Graphical representation of longitudinal waves is the variation of pressure (y-axis) with the distance (x-axis). We know that, the pressure is higher at the point where the element of medium is compressed and the pressure is low where the element of medium is rarefied.
So, the wave forms a pressure peak at compression and pressure valley at rarefaction.

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

In the graphical presentation as attached, what does the valley of wave known as

  1. Compression

  2. Rarefaction

  3. Reflection

  4. Deflection
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Graphical representation of longitudinal waves is the variation of pressure (y-axis) with the distance (x-axis). We know that, the pressure is higher at the point where the element of medium is compressed and the pressure is low where the element of medium is rarefied.
So, the wave forms a pressure peak at compression and pressure valley at rarefaction.

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

A longitudinal waves consists of

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
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. 

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

In case of longitudinal waves, the particles of medium vibrate

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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? 

  1. 0.325 ms

  2. 3.25 ms

  3. 32.5 ms

  4. 325 ms
Reveal answer Fill a bubble to check yourself
A Correct answer
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

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

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

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

  1. Longitudinal

  2. Transverse

  3. both

  4. None
Reveal answer Fill a bubble to check yourself
C Correct answer
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.