CBSE Questions for Class 11 Engineering Physics Waves Quiz 5 - MCQExams.com

$$P$$ is the junction of two wires $$A$$ and $$B$$. $$B$$ is made of steel and is thicker while $$A$$ is made of aluminium and is thinner as shown. If a wave pulse as shown in the figure approaches $$P$$, the reflected and transmitted waves from $$P$$ are respectively :
139731_7a2b955627324633b7377e8d5487137d.jpg
Equations of motion in the same direction is given by
$$y_1 = A\sin(\omega t - kx)$$, $$\space y_2 = A\sin(\omega t - kx - \theta)$$. The amplitude of the medium particle will be
  • $$\sqrt2\ A\cos\theta$$
  • $$2A\cos\theta$$
  • $$\sqrt2A\cos\dfrac{\theta}{2}$$
  • $$2A\cos\dfrac{\theta}{2}$$
Two waves of equal amplitude $$x_0$$ and equal frequency travel in the same direction in a medium. The amplitude of the resultant wave is 
  • $$0$$
  • $$x_0$$
  • $$2x_0$$
  • Between $$0$$ and $$2x_0$$
  • Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
  • Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
  • Assertion is correct but Reason is incorrect
  • Assertion is incorrect but Reason is correct
Two waves of same frequency but amplitudes equal to $$a$$ and $$2a$$ travelling in the same direction superimpose out of phase. The resultant amplitude will be
  • $$\sqrt{a^2+2a^2}$$
  • $$3a$$
  • $$2a$$
  • $$a$$
A wave of frequency $$400\space Hz$$ has a velocity of $$320\space ms^{-1}$$. The distance between the particles differing in phase by $$90^{\small\circ}$$ is
  • $$80\space cm$$
  • $$60\space cm$$
  • $$40\space cm$$
  • $$20\space cm$$
Two sound waves are represented by the following equations 
$$\quad y_1 = 10\sin(3\pi - 0.03x)$$ and 
$$\quad y_2 = 5\sin(3\pi t - 0.03x) + 5\sqrt3\cos(3\pi t - 0.03 x)$$
Then, the ratio of their amplitudes is given by
  • $$1:1$$
  • $$1:2$$
  • $$2:1$$
  • $$2:5$$
Two wires with different densities are joined at $$x = 0$$. An incident wave $$Y_i = A_i\sin(\omega t -k_1x)$$ travelling from left to right is partially reflected and partially transmitted $$(Y_t = A_t\sin(\omega t -k_2x))$$ at $$x = 0$$. If the amplitude of transmitted wave is $$A_t$$ then $$^{\Large A_t}/_{\Large A_i}$$ is
  • $$\displaystyle\frac{2k_1}{k_1+k_2}$$
  • $$\displaystyle\frac{2k_2}{k_1+k_2}$$
  • $$\displaystyle\frac{k_1-k_2}{k_1+k_2}$$
  • $$\displaystyle\frac{\sqrt{k_1}-\sqrt{k_2}}{\sqrt{k_1}+\sqrt{k_2}}$$
If the frequency of a sound wave is doubled then the velocity of sound will be
  • zero
  • half
  • double
  • unchanged
A boat at anchor is rocked by a wave whose crests are $$100\space m$$ apart and whose velocity is $$25\space ms^{-1}$$.how often does the crest reach the boat?
  • $$2500\space s$$
  • $$1500\space s$$
  • $$4.0\space s$$
  • $$0.25\space s$$
For a pulse moving in a heavy string the junctions of the string behaves as a 
  • perfectly rigid end
  • free end
  • partially rigid end
  • rigid end
The wavelength of a sound wave is reduced by 50%. Then the percentage change in its frequency will be
  • 100%
  • 200%
  • 400%
  • 800%
A rod $$70\space cm$$ long is clamped from middle. The velocity of sound in the material of the rod is $$3500\space ms^{-1}$$. The frequency of fundamental note produced by it is :
  • $$3500\space Hz$$
  • $$2500\space Hz$$
  • $$1250\space Hz$$
  • $$700\space Hz$$
A sonometer wire, $$100\ \text{cm}$$ in length has a fundamental frequency of $$330\ \text{Hz}$$. The velocity of propagation of transverse waves along this wire is :
  • $$330\ \text{ms}^{-1}$$
  • $$660\ \text{ms}^{-1}$$
  • $$115\ \text{ms}^{-1}$$
  • $$990\ \text{ms}^{-1}$$
If the wavelength of a wave is decreased by $$20\mbox{%}$$ then its frequency will become :
  • $$20\mbox{%}\space less$$
  • $$25\mbox{%}\space more$$
  • $$20\mbox{%}\space more$$
  • $$25\mbox{%}\space less$$
A wave represented by $$y = 100\sin(ax+bt)$$ is reflected from a dense plane at the origin. If $$36\mbox{%}$$ of energy is lost and rest of the energy is reflected then the equation of the reflected wave will be:
  • $$y = -80\sin(ax+bt)$$
  • $$y = -8.1\sin(ax+bt)$$
  • $$y = -10\sin(ax+bt)$$
  • $$y = -8.2\sin(ax+bt)$$
An ultrasonic scanner is used in a hospital to detect tumours in tissue. The working frequency of the scanner is 4.2 mega Hz. The velocity of sound in the tissue is $$1.7 kms^{-1}$$. The wavelength of sound in the tissue is nearest to 
  • $$\displaystyle 4 \times 10^{-3}$$ m
  • $$\displaystyle 8 \times 10^{-3}$$ m
  • $$\displaystyle 4 \times 10^{-4}$$ m
  • $$\displaystyle 8 \times 10^{-4}$$ m
In a Kundt's tube experiment, the heaps of lycopodium powder are collected at $$20\ cm$$ separations. The frequency of tuning fork used is
  • $$660\ Hz$$
  • $$825\ Hz$$
  • $$775\ Hz$$
  • $$915\ Hz$$
The equation of a plane progressive wave is $$ y=0.9 sin 4\pi[t-\dfrac{x}{2}] $$. When it is reflected at a rigid support, its amplitude becomes $$\dfrac{2}{3} $$ of its previous value. The equation of the reflected wave is 
  • $$ y=0.6 sin 4\pi[t+\dfrac{x}{2}] $$
  • $$ y=-0.6 sin 4\pi[t+\dfrac{x}{2}] $$
  • $$ y=-0.9 sin 8\pi[t-\dfrac{x}{2}] $$
  • $$ y=-0.9 sin 4\pi[t+\dfrac{x}{2}] $$
A series of ocean waves, each 5.0 m from crest to crest, moving past the observer at a rate of 2 waves per second. What is the velocity of ocean waves?
  • 2.5 m/s
  • 5.0 m/s
  • 8.0 m/s
  • 10.0 m/s
If two waves of same frequency and same amplitude, on superposition, produce a resultant disturbance of the same amplitude, the wave differ in phase by
  • $$\pi $$
  • $$2\pi/3$$
  • $$zero$$
  • $$\pi/3$$
The displacement $$y$$ in centimeters is given in terms of time $$t$$ in second by the equation: $$y=3\sin 3.14t+4\cos 3.14 t$$, then the amplitude of SHM is
  • 3 cm
  • 4 cm
  • 5 cm
  • 7 cm
The equation of displacement of a harmonic oscillator is $$x=3\sin{\omega t}+4\cos{\omega t}$$. The amplitude of the particles will be
  • 1
  • 5
  • 7
  • 12
If the frequency of a sound wave is increased by 25%, then the change in its wavelength will be
  • 25% decrease
  • 20% decrease
  • 20% increase
  • 25% increase
A sound wave of frequency $$500\ \text{Hz}$$ covers a distance of  $$1000\ \text{m}$$ in $$5\ \text{s}$$ between points $$\displaystyle x$$ and $$\displaystyle y$$. Then the number of waves between $$\displaystyle x$$ and $$\displaystyle y$$ are
  • 5000
  • 2500
  • 100
  • 500
Interference event is observed
  • only in transverse waves
  • only in longitudinal waves
  • in both types of waves
  • none
Two particles are executing $$S.H.M$$ of same amplitude and frequency along the same straight line path. They pass each other when going in opposite directions, each time their displacement is half of their amplitude. What is the phase difference between them?
  • $$5\pi/6$$
  • $$2\pi/3$$
  • $$\pi/3$$
  • $$\pi/6$$
The equation $$ y=A sin^2(kx-\omega t) $$ represents a wave with
  • amplitude A frequency $$\omega/2\pi $$
  • amplitude A /2 frequency $$\omega/\pi $$
  • amplitude 2A frequency $$\omega/4\pi $$
  • It does not represent a wave motion
The phenomenon of interference is shown by
  • longitudinal mechanical waves only
  • transverse mechanical waves only
  • non-mechanical transverse waves only
  • All of the above
Statement 1: A transverse  wave are produced in a very long string fixed at one end. Only progressive wave is observed near the free end.
Statement 2: Energy of reflected wave does not reach the free end
  • Statement-1 is false, Statement -2 is true
  • Statement-1 is true, Statement-2 is true; Statement-2 is a correct explanation for Statement-1
  • Statement-1 is true, Statement-2 is true; Statement-2 is not a correct explanation for statement-1
  • Statement-1 is true, Statement-2 is false
The frequency of light of wave length $$5000\ {\buildrel_{\circ}\over {A}}$$ is:
  • $$1.5 \times 10^3\ Hz$$
  • $$6 \times 10^8\ Hz$$
  • $$6 \times 10^{14}\ Hz$$
  • $$7.5 \times 10^{15}\ Hz$$
The displacement of a particle varies according to the relation $$ x=4(cos \pi t+ sin \pi t)$$. The amplitude of the particle is
  • $$ -4 m $$
  • $$ 4 m $$
  • $$ 4\sqrt{2} m $$
  • $$ 8m $$
A particle executing simple harmonic motion along y-axis has its motion described by the equation $$y = A\sin(\omega t) + B$$. The amplitude of the simple harmonic motion is:
  • $$A$$
  • $$B$$
  • $$A+B$$
  • $$\sqrt{A+B}$$
Consider a sinusoidal travelling wave shown in figure. The wave velocity is $$+ 40 cm/s$$. Find the frequency.
212519_b05464a239e5466d83a0028f8e916670.png
  • $$2 Hz$$
  • $$6 Hz$$
  • $$8 Hz$$
  • $$10 Hz$$
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 :
  • $$4\lambda$$
  • $$\lambda $$
  • $$\lambda/4 $$
  • $$ 16\lambda $$
A string of length $$20\  cm$$ and linear mass density $$0.4\  g/cm$$ is fixed at both ends and is kept under a tension of $$16 \ N$$. A wave pulse is produced at $$t = 0$$ near an end as shown in figure which travels towards the other end. The string have the shape shown in the figure again in $$ 2 \times 10^{-x} sec$$. Find $$x$$.
212632_790d8e9eb7d942678be19e0955ee4b6e.png
  • $$1$$
  • $$2$$
  • $$8$$
  • $$3$$
State whether the given statement is True or False :
Consider a sinusoidal travelling wave shown in figure. The wave velocity is $$+ 40 cm/s$$. The phase difference between points  $$2.5\  cm$$ apart will be $$\dfrac{5\pi}{4}$$ rad.

212524_0b2182e6f5b54784aa397b60c1d9528b.png
  • True
  • False
Two waves are travelling in the same direction along a stretched string. The waves are $$90^0$$ out of phase. Each wave has an amplitude of 4.0 cm. The amplitude of the resultant wave is $$5.66 \times 10^{-x} m$$. Find x. 
  • 1
  • 2
  • 8
  • 4
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
  • $$\displaystyle \frac{\pi}{2}$$
  • $$\pi$$
  • $$2 \pi$$
  • $$\displaystyle \frac{\pi}{4}$$
The period of a particle in SHM is $$8 s$$. At $$t=0$$ it is in its equilibrium position. Find the ratio of the distance traveled in the first $$2 s$$ and the next $$2 s$$.
  • $$3$$
  • $$5$$
  • $$2$$
  • $$1$$
Three coherent waves having amplitudes 12 mm, 6 mm and 4 mm arrive at a given point with successive phase difference of $$\pi/2$$. Then the amplitude of the resultant wave is
  • 7 mm
  • 10 mm
  • 5 mm
  • 4.8 mm
A wave travels on a light string. The equation of the waves is $$Y\, = \,A\, sin\,(kx\,-\,\omega\,t+\,30^{\circ})$$. It is reflected from a heavy string tied to end of the light string at x = 0 . If 64% of the incident energy is reflected then the equation of the reflected wave is  
  • $$Y\, =\,0.8 \,A\, sin\,(kx\,-\,\omega\,t\,+\,30^{\circ}\,+\,180^{\circ})$$
  • $$Y\, =\,0.8 \,A\, sin\,(kx\,+\,\omega\,t\,+\,30^{\circ}\,+\,180^{\circ})$$
  • $$Y\, =\,0.8 \,A\, sin\,(kx\,-\,\omega\,t\,-\,30^{\circ})$$
  • $$Y\, =\,0.8 \,A\, sin\,(kx\,-\,\omega\,t\,+\,30^{\circ})$$
A source oscillates with a frequency 25 Hz and the wave propagates with 300 m/s. Two points A and B are located at distances 10 m and 16 m away from the source. The phase difference between A and B is 
  • $$\displaystyle \frac{\pi}{4}$$
  • $$\displaystyle \frac{\pi}{2}$$
  • $$\pi$$
  • $$2 \pi$$
Three one dimensional mechanical waves in an elastic medium is given as and
$$y_1\,=\,3A \,sin\,(\omega\,t\,-\,kx)$$
$$y_2\,=\,A \,sin\,(\omega\,t\,-\,kx\,+\,\pi)$$
$$y_3\,=\,2A \,sin\,(\omega\,t\,+\,kx)$$ 
are superimposed with each other. The maximum displacement amplitude of the medium particle would be 
  • 4A
  • 3A
  • 2A
  • A
Vibrations of period 0.25 s propagate along a straight line at a velocity of 48 cm/s. One second after the emergence of vibrations at the initial point, displacement of the point, 47 cm from it is found to be 3 cm. Then,
  • amplitude of vibrations is 6 cm.
  • amplitude of vibrations is $$3 \sqrt{2} cm.$$
  • amplitude of vibrations is 3 cm.
  • None of the above
A body is vibrating 7200 times in one minute. If the velocity of sound is 360 m/s, find (i) frequency of the vibration in Hz, (ii) the wavelength of the sound produced.
  • $$120\ Hz, 3\ m$$
  • $$140\ Hz, 3\ m$$
  • $$120\ Hz, 4\ m$$
  • $$140\ Hz, 4\ m$$
A .......... is any disturbance that transmits energy without carrying any material with it.
269427.jpg
  • Wave
  • Temperature
  • Vibration
  • Echolocation
A particle moves on the X-axis is according to the equation $$x = A+B\space \sin\omega t$$. The motion is simple harmonic with amplitude:
  • $$A$$
  • $$B$$
  • $$A+B$$
  • $$\sqrt{A^2 + B^2}$$
Sound travels with a speed of about 330m/s. What is the wavelength of sound whose frequency is 660 Hz?
  • 0.5 m
  • 1 m
  • 2 m
  • 1.5 m 
Which of the following parameters of a wave undergoes a change when wave is reflected from a boundary ?
  • $$Intensity$$
  • $$Phase$$
  • $$Speed$$
  • $$Frequency$$
0:0:1


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