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 structure of earth seismic waves and tsunami causes of earthquakes origin of earth and its internal energy transfer of charge lightning safety

An earthquake generates both transverse $(S)$ and longitudinal $(P)$ sound waves in the earth. The speed of $S$ waves is about $4 \,\,km \,\,s^{-1}$ and that of $P$ waves is about $8 \,\,km \,\,s^{-1}$. A seismograph records $P$ and $S$ waves from an earthquake.The first $P$ wave arrives $4$ min before the first $S$ wave. The epicentre of the earthquake is located at a distance of about

  1. $192 km$
  2. $384 km$
  3. $1920 km$
  4. $3840 km$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Let $\nu _1, \nu _2$ be speed $S$ of $S$ and $P$ waves and $t _1,t _2$ be the time taken by these waves to travel to reach the seismograph. Let the epicenter of the earthquake is located at a distance $d$ from the seismograph. Then,
$d = V _1 t _1 = V _2 t _2$          ................ .....(i)
Here, $V _1 = 4 km \,\,s^{-1}$ and $V _2 = 8 km \,\,s^{-1}$
$\therefore 4t _1 = 8t _2 \Longrightarrow t _1 = 2t _2$           ....(ii)
and  $t _1 - t _2 = 4 min = 240 s$
$\therefore 2t _2 - t _2 = 240$      ....................  [using (ii)]
or $t _2 = 240 s$
put in Eq. (ii), we get,
$t _1 = 2 \times 240 s = 480 s$
From Eq. (i), we get, $d = (4 km \,\,s^{-1}) (480 s) = 1920 km$
Multiple choice physics structure of earth seismic waves and tsunami causes of earthquakes origin of earth and its internal energy transfer of charge lightning safety

Choose the correct statement.

  1. 'P' waves are slower than 'S' waves.

  2. Both 'P' and 'S' waves have same speed.

  3. 'S' waves are slower than 'P' waves.

  4. None of the above.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
The P waves and the S waves are the waves that travel throughout the planet. The P waves are the compression waves that apply force in the direction of propagation whereas the S waves are shear waves that make the medium particle move perpendicular to their direction of motion.
The energy is less easily transmitted in the medium in the case of S waves. So, P waves travel faster.

Option $C$ is correct.
Multiple choice physics study of sound types of waves sound as a wave of disturbance sound waves are longitudinal waves

The longitudinal wave can be observed in

  1. Elastic media

  2. inelastic media
  3. Both $(1)$ & $(2)$

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

Longitudinal waves travel only in the elastic medium. These waves comprise of compressions and rarefactions. The speed of Longitudinal waves is given by :

$v=\dfrac{\sqrt{B}}{\rho }$ where B is the bulk modulus of elasticity and $\rho $ is the density of the medium

Multiple choice physics study of sound types of waves sound as a wave of disturbance sound waves are longitudinal waves

A transverse wave along a string is given by y=$2\sin \left( {2\pi \left( {3t - x} \right) - \frac{\pi }{6}} \right)$, where x and y are in cm and 't' is in second. The acceleration of a particle located at x=4cm at t =1s is 

  1. $36\pi ^2$
  2. $72\pi ^2$
  3. $18\pi ^2$
  4. $12\pi ^2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The wave equation is y = 2 sin(6*pi*t - 2*pi*x - pi/6). Velocity v = dy/dt = 2 * 6*pi * cos(6*pi*t - 2*pi*x - pi/6). Acceleration a = dv/dt = -2 * (6*pi)^2 * sin(6*pi*t - 2*pi*x - pi/6). At x=4 and t=1, the argument is 6*pi - 8*pi - pi/6 = -2*pi - pi/6. sin(-2*pi - pi/6) = sin(-pi/6) = -1/2. Thus, a = -2 * 36*pi^2 * (-1/2) = 36*pi^2.

Multiple choice physics study of sound types of waves sound as a wave of disturbance sound waves are longitudinal waves

The waves in which the particles of the medium travel in the same direction as the waves are called :

  1. linear waves

  2. longitudinal waves

  3. transverse waves

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

The waves in which the particles of the medium travel in the same direction as the waves are called longitudinal waves. 

Example:sound waves, seismic waves.

Multiple choice physics study of sound types of waves sound as a wave of disturbance sound waves are longitudinal waves

Wave on water surface are

  1. Longitudinal

  2. Transverse

  3. Combination of longitudinal and transverse.

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

$Answer:-$ C option

Ocean waves are both longitudinal and transverse. Technically, they're a special category called surface waves. 

At the surface of the water (or generally any place two fluids of different densities meet) the force of gravity acts as the "returning" force required for transverse waves to propagate. Gravity wants to level out the surface of the water, so peaks try to flatten and troughs try to fill. This is somewhat similar to the way a guitar string tries to return to a straight line after being plucked. 

However there is essentially zero shear strength in water, so pure transverse waves would die out extremely quickly. The trick comes from the fact that the water in an ocean wave does not move with the wave itself -- each bit of water can only give its neighbors a push, not flow. This push increases the local pressure in the water, which allows the wave to become deeper/higher.

If you could see the bulk pressure/motion of the water column below the surface, you would immediately see the fact that the "wave" is mostly a localized upswell caused by an actual submerged longitudinal pressure wave. Or you could say the upswell from the wave causes a submerged longitudinal pressure wave beneath it! Two ways to say the same thing. Dynamic fluid behavior is tricky like that. 

Multiple choice physics study of sound types of waves sound as a wave of disturbance sound waves are longitudinal waves

The waves produced by a motor boat sailing in water are

  1. transverse

  2. longitudinal

  3. longitudinal and transverse

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

When a motor boat sails in water , waves will be produced on the surface of the water. We know that water waves are a combination of longitudinal and transverse waves as the particles move in a circular path.    

Multiple choice physics study of sound types of waves sound as a wave of disturbance sound waves are longitudinal waves

Energy is not carried by 

  1. Transverse progressive waves

  2. Longitudinal progressive waves

  3. Stationary waves

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

$Answer:-$ C option

All the propagating waves (wave on string -transverse , sound-longitudinal)  carry energy with them and also electromagnetic waves like light carry energy.
Stationary waves do not carry energy with them because their energy is confined in that area (as they are not propagating).

Multiple choice physics study of sound types of waves sound as a wave of disturbance sound waves are longitudinal waves

Waves inside a gas are

  1. Longitudinal

  2. Transverse

  3. Partly longitudinal, partly transverse.

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

$Answer:-$ A option

In fluids (liquids and gases), atoms have no "equilibrium location"; they can move freely past each other. So if one atom gets moved by a disturbance, there's no restoring force to pull it back to its equilibrium location,
hence transverse waves cannot travel through fluids.
so only longitudinal waves can travel in gases and liquids.

Multiple choice physics study of sound types of waves sound as a wave of disturbance sound waves are longitudinal waves

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

  1. Longitudinal waves

  2. Propagated waves

  3. Transverse wave

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

Transverse waves have particles oscillating perpendicular to the direction of motion of wave. Ripple in the surface of water is transverse in nature

Multiple choice physics study of sound types of waves sound as a wave of disturbance sound waves are longitudinal waves

The waves which can propagate in metals are :

  1. longitudinal waves

  2. transverse waves

  3. both (a) and (b)

  4. neither (a) nor (b)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Propagation of waves depends on the medium through which they propagate. Transverse wave need a medium rigid enough which neither liquid nor gas can provide and hence transverse wave can travel through metals. For longitudinal wave they just require a medium for propagation. Hence transverse and longitudinal wave can both propagate in metals.