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

When slinky is stretched out in a horizontal direction and first coils are vibrated horizontally then which waves are generated?

  1. Longitudinal Waves

  2. Transverse Waves

  3. Surface waves

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

Longitudinal Waves are generated when slinky is stretched out in a horizontal direction and first coils are vibrated horizontally 

Multiple choice physics wave optics wave behaviour huygens wave theory and wavefront wave propagation (huygens' construction)

Wave front means:

  1. all particles in it have same phase

  2. few particles are in same phase, rest are in opposite phase

  3. all particles have opposite phase of vibrations

  4. all particles have random vibrations
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

All particles in it have same phase.

It is the imaginary surface representing corresponding points pf a wave that vibrate in unison. When identical waves having a common origin travel through a homogeneous medium , the corresponding crests and troughs at any instant phase.

Multiple choice physics wave optics wave behaviour huygens wave theory and wavefront wave propagation (huygens' construction)

A wavefront is an imaginary surface where :

  1. phase is same for all points

  2. phase changes at constant rate at all points along the surface

  3. constant phase difference continuously changes between the points

  4. phase changes all over the surface
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A wave front is the locus of points having the same phase.
Hence option A is correct.

Multiple choice physics wave optics wave behaviour huygens wave theory and wavefront wave propagation (huygens' construction)

The wavefront is a surface in which

  1. all points are in the same phase

  2. there is a pair of points in opposite phase
  3. there is a pair of points with phase difference $(\dfrac{\pi}{2})$

  4. there is no relation between the phases
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A wavefront is the locus of points characterized by propagation of position of the same phase: a propagation of a line in 1D, a curve in 2D or a surface for a wave in 3D.

Multiple choice problems on properties of waves terms and defination used in wave motion oscillation and waves waves physics

The particle of a medium vibrates about their mean position whenever a wave travels through that medium. The phase difference between the vibrations of two such particles

  1. varies with time only

  2. varies with distance separating them only

  3. varies with time as well as distance

  4. is always zero
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The phase difference between the vibrations of two particles of the medium is given by :

            $\Delta \phi=\dfrac{2\pi}{\lambda}\Delta x$ 
it is clear that phase difference varies as the path difference between the particles varies, which is the distance, separating the particles.

Multiple choice problems on properties of waves terms and defination used in wave motion oscillation and waves waves physics

Two Waves of amplitudes ${ A } _{ 0 }$ and $x{ A } _{ 0 } $ pass through a region. If x >1, the difference in the maximum and minimum resultant amplitude possible is

  1. $(x+1){ A } _{ 0 }$
  2. $(x-1){ A } _{ 0 }$
  3. $2x{ A } _{ 0 }$
  4. $2{ A } _{ 0 }$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Maximum amplitude A_max = A1 + A2 = (x + 1) * A_0. Minimum amplitude A_min = |A1 - A2| = (x - 1) * A_0. The difference is A_max - A_min = (x + 1) * A_0 - (x - 1) * A_0 = 2 * A_0.

Multiple choice problems on properties of waves terms and defination used in wave motion oscillation and waves waves physics

The equation of a wave is given by $Y\, =\, 5\, sin\, 10 \pi\, (t\, -\, 0.01x)$ along the x-axis. (All the quantities are expressed in SI units}. The phase difference the points separated by a distance of 10 m along x-axis is

  1. $\displaystyle \frac{\pi}{2}$
  2. $\pi$
  3. $2 \pi$
  4. $\displaystyle \frac{\pi}{4}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For the given wave, $k=0.1\pi=\dfrac{2\pi}{\lambda}$
$\implies \lambda=20m$

Thus phase difference between two points separated by 10m is $\dfrac{2\pi}{\lambda}(x _2-x _1)$
$=\dfrac{2\pi}{\lambda}\times 10m=\pi$
Hence correct answer is option B.

Multiple choice problems on properties of waves terms and defination used in wave motion oscillation and waves waves physics

When a wave travels in a medium, the particle displacement is given by y(xt)=0.03 sin $\pi $ (2t-0.01 x) where y and x are meters and t in seconds. The phase difference, at a given instant of time between two particle 25 m. apart in the medium, is 

  1. $\frac{\pi }{8}$
  2. $\frac{\pi }{4}$
  3. $\frac{\pi }{2}$
  4. $\pi$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The phase difference delta phi is given by (2pi / lambda) * delta x, or from the wave equation k * delta x. Here k = 0.01 pi, so delta phi = 0.01 pi * 25 = 0.25 pi = pi / 4 radians.

Multiple choice problems on properties of waves terms and defination used in wave motion oscillation and waves waves physics

The light waves from two independent monochromatic light sources are given by-
${y _1} = 2\sin  {\omega t }$ and ${y _2} = 2\cos  {\omega t }$,
then the following statement is correct 

  1. Both the waves are coherent

  2. Both the waves are incoherent

  3. Both the waves have different time periods

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

${y _1} = 2\sin \left( {\omega t - kx} \right)$
${y _2} = 2\cos \left( {\omega t - kx} \right) = 2\sin \left( {\omega t - kx + \frac{\pi }{2}} \right)$
So, Phase difference = $\frac{\pi}{2}$
Hence sources are incoherent.

Multiple choice problems on properties of waves terms and defination used in wave motion oscillation and waves waves physics

The phase difference between two points is $\pi/3$. If the frequency of wave is 50 Hz, then what is the distance between two points? (given v = 330 m/s)

  1. 2.2 m

  2. 1.1 m

  3. 0.6 m

  4. 1.7 m
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Phase difference $= \dfrac{2\pi}{\lambda}\times$path difference. 
The phase difference between any two particles in a wave determines lack of harmony in the vibrating state of two particles ie, how far one particle leads the other or lags behind the other. 
From relation 
$\Delta \phi =\dfrac{2\pi}{\lambda}\times \delta x$


$\Rightarrow \Delta x = \dfrac{\lambda}{2\pi}\times \Delta \phi$    ...(i)

Also, $\lambda = \dfrac{v}{n}$      ...(ii)
Now, from Eqs. (i) and (ii), we get
$\Delta x=\dfrac{v}{2\pi n}\times \Delta \phi$

$\Rightarrow \Delta x=\dfrac{330}{2\pi\times 50}\times \dfrac{pi}{3}$
or $\Delta x = 1.1m$ 

Multiple choice problems on properties of waves terms and defination used in wave motion oscillation and waves waves physics

When a transverse wave on a string is reflected from the free end, the phase change produced is ___________.

  1. Zero rad
  2. $\dfrac { \pi }{ 2 } $ rad
  3. $\dfrac { 3\pi }{ 4 } $ rad
  4. $\pi$ rad
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For a transverse wave, a phase change of $\pi$ occurs when it is reflected from a denser medium.

When reflected from a free end, however, there is no change of phase.
Hence the correct answer is option A.