Physics

Wave Motion

536 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 medical imaging ultrasonic sound using ultrasound in medicine ultrasound and its applications

What is the wavelength of the ultrasound in water ?

  1. $1.5 mm$
  2. $3.0 cm$
  3. $4.5 cm$
  4. $6.0 cm$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The frequencies used in ultrasonic diagnosis are in the range of 1 to 10 MHz. The speed of sound waves in the tissues of the human body averages about 1540 m/s (close to that for water). So, the wavelength of a 1 MHz wave is about $λ = v/f = 1540/1∙106 = 1.5∙10–3 m = 1.5 mm$.

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

The distance between tow adjacent particles which are in the same phase in a progressive wave is 20 cm. determine the velocity of the wave if its frequency is 10 Hz.

  1. $2 {ms}^{-1}$
  2. $40 {ms}^{-1}$
  3. $8 {ms}^{-1}$
  4. $80 {ms}^{-1}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The distance between two adjacent particles in the same phase is the wavelength (lambda). Given lambda = 20 cm = 0.2 m and frequency f = 10 Hz, the velocity v = f * lambda = 10 * 0.2 = 2 m/s.

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

A wave has a frequency of $5$ GHz.
What is the period of the wave?

  1. $200$ ps
  2. $0.2$ ns
  3. $20$ ns
  4. $20000$ $\mu s$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Given that,


Frequency $f=5 GHz=5\times10^{9}\ Hz$


The period of the wave is reciprocal of frequency.

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

$T=\dfrac{1}{5\times10^{9}}$

$T=2\times10^{-10}$

$T=0.2\ ns$

The period of the wave is $0.2\ ns$

Hence, B is correct option.

Multiple choice physics option a: relativity maxwell's equations the nature of light introduction to electromagnetic waves

Choose the correct answer from the alternatives given.
A plane electromagnetic wave of frequency $25 MHz$ travels in free space along $X$-direction. At a particular point in space and time, electric field $\vec E=6.3\ \hat j\ V/m$. What is $B$ at this point.

  1. $1.2 \, \times \, 10^{-6} \, T$
  2. $1.2 \, \times \, 10^{-8} \, T$
  3. $2.1 \, \times \, 10^{-6} \, T$
  4. $2.1 \, \times \, 10^{-8} \, T$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Given: The frequency of the electromagnetic wave is $25\ MHz$.

The electric field at the particular point is $6.3\hat j\ V/m$

To find: The magnetic field at that point.

The magnetic field of the electromagnetic wave at a point is given by:
$B = \dfrac{E}{c}\= \dfrac{6.3}{3 \times 10^8}\ \Rightarrow2.1 \times 10^{-8} T$

So, option $(D)$ is correct.

Multiple choice physics world of sounds sound produced by humans propagation of sound production and propagation of sound

The physical quantity which oscillates in most waves is:

  1. Mass

  2. Energy

  3. Amplitude

  4. Wavelength
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Mass of a particle executing a vibration in a wave is constant. The energy and wavelength in a wave in the same medium remain constant. Amplitude of the wave varies with time although the peak value of  the amplitude is constant.

Multiple choice multiple-slit diffraction the principle of superposition of waves superposition of waves oscillations and waves physics

In the above question, the intensity of the waves reaching a point P far away on the x-axis from each of the four sources is almost the same and equal to $I _0.$ Then,

  1. If $d=\lambda /4,$ the intensity at P is $4I _0.$
  2. If $d=\lambda /6,$ the intensity at P is $3I _0.$
  3. If $d=\lambda /2,$ the intensity at P is $3I _0.$

  4. None of these is true
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice multiple-slit diffraction the principle of superposition of waves superposition of waves oscillations and waves physics

The phase difference between two waves from successive half period zones or strips is :

  1. $\dfrac{\pi}{ 4}$
  2. $ \dfrac{\pi}{ 2}$
  3. $ \pi $

  4. zero
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The half period zone is provided by an optical device known as zone plate. It is simply a plane parallel gloss plate having concentric circles of radii accurately proportional to the square roots of the consecutive natural numbers 1,2,3 ... etc. The area is given by $\pi \gamma ^{2}$. Hence the
areas are $\pi , 2\pi , 3\pi , 4\pi$,---
The phase difference is thus $\pi$ between each successive half period zones of strips.

Multiple choice multiple-slit diffraction the principle of superposition of waves superposition of waves oscillations and waves physics

Let ${a _1}$ and ${a _2}$ be the amplitudes of two light waves of same frequency and ${\alpha _1}$ and ${\alpha _2}$ be their initial phases. The resultant amplitude due to the superposition of two light waves is

  1. $R = \sqrt {a _1^2 + a _2^2 + 2{a _1}{a _2}} $
  2. $R = {a _1} - {a _2}$
  3. $R = \sqrt {a _1^2 + a _2^2 + 2{a _1}{a _2}\cos \left( {{\alpha _1} - {\alpha _2}} \right)} $
  4. $R = \sqrt {a _1^2 + a _2^2 - 2{a _1}{a _2}} $
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The angle between two light waves $={ \alpha  } _{ 1 }-{ \alpha  } _{ 2 }$

Resultant $=\sqrt { { a } _{ 1 }^{ 2 }+{ a } _{ 2 }^{ 2 }+2{ a } _{ 1 }.{ a } _{ 2 }\cos { ({ \alpha  } _{ 1 }-{ \alpha  } _{ 2 }) }  } $

Multiple choice multiple-slit diffraction the principle of superposition of waves superposition of waves oscillations and waves physics

In the interference of waves from two sources of intensities $I _o$ and $4I _o$, the intensity at a point where the phase difference is $\pi$, is?

  1. $I _o$
  2. $2I _o$
  3. $3I _o$
  4. $4I _o$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$I=I _1+I _2+2\sqrt{I _1I _2}\cos\theta =I _o+4I _o+2\sqrt{(I _o\times 4I _o)}\cos\pi =I _o$
Hence (A) is correct.

Multiple choice multiple-slit diffraction the principle of superposition of waves superposition of waves oscillations and waves physics


The displacement of two interfering light wave are $ y _1 = 4 sin \omega t and y _2 = 3 cos(\omega t) $
The amplitude of the resultant wave is and $ y _2 $ are:(in CGS system)

  1. 5 cm

  2. 7 cm

  3. 1 cm

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

Given that,

$ {{y} _{1}}=4\sin \omega t $

$ {{y} _{2}}=3\cos \omega t $

Amplitude of first and second wave is 4 cm and 3 cm. So, the amplitude of resultant wave is

$ {{y}^{'}}=\sqrt{{{(4)}^{2}}+{{(3)}^{2}}} $

$ =5\,cm $

Multiple choice multiple-slit diffraction the principle of superposition of waves superposition of waves oscillations and waves physics

Two coherent waves are represented by $y _1=a _1\cos\omega t$ and $y _2=a _2\cos\omega t$. The maximum intensity due to interference will be proportional to

  1. $(a _1+a _2)$
  2. $(a _1-a _2)$
  3. $(a^2 _1+a^2 _2)$
  4. $(a^2 _1-a^2 _2)$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

 $intensity \ \alpha \ (amplitude)^{2}$
so maximum intensity is proportional to $a^{2} _{1}+a^{2} _{2}$
option $C$ is correct 

Multiple choice multiple-slit diffraction the principle of superposition of waves superposition of waves oscillations and waves physics

Two identical light waves, propagating in the same direction, have a phase difference $\delta $. After they superpose the intensity of the resulting wave will be proportional to

  1. $\cos { \delta } $
  2. $\cos { \left( \dfrac { \delta }{ 2 } \right) } $
  3. $\cos ^{ 2 }{ \left( \dfrac { \delta }{ 2 } \right) } $
  4. $\cos ^{ 2 }{ \delta } $
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Maximum intensity,
     $I=4{ I } _{ 0 }\cos ^{ 2 }{ \left( \dfrac { \delta  }{ 2 }  \right)  } $
$\Rightarrow I\propto \cos ^{ 2 }{ \left( \dfrac { \delta  }{ 2 }  \right)  } $