Physics - Waves
Exam Duration: 45 Mins Total Questions : 30
Choose the INCORRECT statement
- (a)
Audibility range of a human ear is 20 Hz to 20 kHz
- (b)
Linear distance between the successive points which are in the same phase is half of the length of a wave
- (c)
The temperature at which velocity of sound in air is double its velocity at \({ 0 }^{ \circ }C\) is \(819^{ \circ }C\)
- (d)
The velocity of sound increases with increase of humidity
In the formation of beats due to superposition of two wavetrains of nearly equal frequencies, the maximum loudness at the waxing is found to be k times the loudness of each component wavetrains. The value of k is
- (a)
1
- (b)
2
- (c)
4
- (d)
8
In a stationary waves,
- (a)
the energy of the waves is zero
- (b)
the energy in the medium is zero
- (c)
the energy transfer in the direction of propagation is zero
- (d)
the energy density of the waves is constant
A wave is represented by the equation
\(y\quad =\quad a\quad sin\quad (\omega t\quad -\quad kx)\)
The maximum particle velocity will be four times wave velocity if ak is equal to
- (a)
1
- (b)
2
- (c)
3
- (d)
4
At a distance 1.5 m from a small loudspeaker, the amplitude of the sound heard is 0.012 mm. At a distance 20 m from the loudspeaker, the amplitude in mm is
- (a)
0.016 mm
- (b)
0.160 mm
- (c)
0.009 mm
- (d)
NONE OF THE ABOVE
In the production of beats by two progressive waves of nearly the same frequency,
- (a)
the frequency of the beats is a function of time
- (b)
the frequency of the beats depends on the relative position of the listener
- (c)
the frequency of beats depends on the relative velocity between the source and listener
- (d)
the frequency of the beats can heard more distinctly if the frequency difference between the component waves is large
Source of sound and observer are moving with the same velocity along the positive direction of x-axis. The medium is moving along the negative direction of x-axis. Let \({ \vartheta }_{ s },{ \quad \vartheta }_{ 0 }\) and w be velocities of source, observer and medium respectively, and \(\nu \quad and\quad { \nu }^{ \prime }\) be the frequency of sound source and the apparent frequency heard by the observer respectively. Then,
- (a)
\({ \nu }^{ \prime }\quad =\quad \nu \)
- (b)
\({ \nu }^{ \prime }\quad =\quad \left( \frac { { \nu }_{ s }-{ \nu }_{ 0 }-w }{ { \nu }_{ s } } \right) \nu \)
- (c)
\({ \nu }^{ \prime }\quad =\quad \left( \frac { { \nu }_{ s }-w }{ { \nu }_{ s } } \right) \nu \)
- (d)
\({ \nu }^{ \prime }\quad =\quad \left( \frac { { \nu }_{ s }+w }{ { \nu }_{ s } } \right) \nu \)
The equation
\(y\quad =\quad a\quad sin\quad \frac { 2\pi }{ \lambda } (\vartheta t+x+{ \phi }_{ 0 })\)
represents
- (a)
a wave, longitudinal or transverse, travelling along minus x-axis
- (b)
a wave, longitudinal or transverse, travelling along positive x-axis
- (c)
a wave, longitudinal or transverse, travelling along y-axis
- (d)
a transverse wave travelling along minus x-axis
Two travelling waves of sound are found to have sinusoidal waveform but different wavelength and different amplitude. They will have
- (a)
same pitch but different intensity
- (b)
same pitch but different quality
- (c)
same quality but different intensity
- (d)
different quality and intensity
The magnitude of threshold of hearing, persistence of hearing and persistence of vision are respectively
- (a)
\({ 10 }^{ -6 }\quad W{ m }^{ -2 },\quad \frac { 1 }{ 5 } s\quad and\quad \frac { 1 }{ 10 } s\)
- (b)
\({ 10 }^{ -10 }\quad W{ m }^{ -2 },\quad \frac { 1 }{ 10 } s\quad and\quad \frac { 1 }{ 25 } s\)
- (c)
\({ 10 }^{ -16 }\quad W{ m }^{ -2 },\quad \frac { 1 }{ 16 } s\quad and\quad \frac { 1 }{ 10 } s\)
- (d)
\({ 10 }^{ -12 }\quad W{ m }^{ -2 },\quad \frac { 1 }{ 10 } s\quad and\quad \frac { 1 }{ 16 } s\)
I organic pipe (or in the resonance apparatus) we have the formation of
- (a)
stationary transverse waves
- (b)
stationary longitudinal waves
- (c)
progressive longitudinal waves
- (d)
progressive transverse waves
The diaphragm of a microphone in front of which a person speaks execute
- (a)
natural (free) vibrations
- (b)
electromagnetic vibrations
- (c)
forced vibrations
- (d)
resonant vibrations
The velocity of sound at high altitudes is less because
- (a)
The ratio \(\sqrt { \frac { P }{ \rho } } \) is less where P and \(\rho \) are the pressure and density of air respectively
- (b)
pressure of air is less
- (c)
temperature of air is less
- (d)
density of air is less
At a point 20 m from a small sources of sound, the density is \(0.5\quad \mu W\quad { cm }^{ 2 }\). The rate of emission of sound energy from the source is
- (a)
25 W
- (b)
\(0.5\quad \mu W\)
- (c)
\(25\quad \mu W\)
- (d)
25 mV
The mechanical waves have in common with electromagnetic waves the essential feature of
- (a)
energy propagation
- (b)
momentum propagation
- (c)
propagation through any meterial substance-solid, lliquid and gas
- (d)
both energy and momentum propagation
Which of the following waves are three-dimensional?
- (a)
Sound waves in air
- (b)
Water waves
- (c)
Water along a taut string
- (d)
waves along a spring
A simple harmonic wave on a taut string with linear density m = 0.10 kg m-1 has a total energy of 4 J per wavelength. The maximum transverse velocity of the string is 15.0 ms-1, which is one half of the propagation velocity of the wave. The wavelength of the wave is
- (a)
35.6 cm
- (b)
4.0 cm
- (c)
17.8 cm
- (d)
21.8 cm
A long thin copper rod is given a sharp compressional blow at one end. The sound of the blow, travelling through air at \({ 0 }^{ \circ }C\), reaches the opposite end of the rod 6.84 ms later than the sound transmitted through the rod. The velocity of sound in copper rod is \(\vartheta { C }_{ u }\quad =\quad 3.750\quad km\quad { s }^{ -1 }\) and velocity of sound in the air at \({ 0 }^{ \circ }C\) is \(\vartheta \quad =\quad 330\quad m{ s }^{ -1 }\). The length of the rod is
- (a)
2.475 km
- (b)
2.475 m
- (c)
2.475 cm
- (d)
NONE OF THE ABOVE
The sonometer wire is vibrating in the second overtone. We may say that there are
- (a)
two nodes and two antinodes
- (b)
one node ant two antinodes
- (c)
four nodes and three antinodes
- (d)
three nodes and three antinodes
A stationary wave is represented by
y = A sin (100 t) cos (0.01 x)
where A and y are in mm t in seconds and x metre. The velocity of the wave is
- (a)
1 ms-1
- (b)
100 ms-1
- (c)
104 ms-1
- (d)
not derivable from the given data
A uniform rope of mass 0.1 kg and length 2.45 m hangs from the ceiling. Find the speed transverse waves at a point 0.5 m distant from the lower end.
- (a)
1.22 ms-1
- (b)
2.21 ms-1
- (c)
22.1 ms-1
- (d)
12.2 ms-1
A simple rod clamped in the middle can be set into longitudinal vibration. What kind of vibrations does it produce when bent to form a turning fork?
- (a)
Transverse
- (b)
Longitudinal
- (c)
Both transverse and longitudinal
- (d)
Transverse or longitudinal depending upon the medium
The relation between phase difference and path difference is
- (a)
\(\triangle \phi \quad =\quad \frac { 2\pi }{ \lambda } (\triangle x)\)
- (b)
\(\triangle \phi \quad =\quad 2\pi \lambda (\triangle x)\)
- (c)
\(\triangle \phi \quad =\quad \frac { 2\pi \lambda }{ \triangle x } \)
- (d)
\(\triangle \phi \quad =\quad \frac { 2\triangle x }{ \lambda } \)
At a certain instant, a stationary transverse wave is found to have maximum kinetic energy. The apperearance of the string that at the instant is
- (a)
sinusoidal shape with amplitude A/2
- (b)
sinusoidal shape with amplitude A/3
- (c)
sinusoidal shape with amplitude A
- (d)
straight line
Three waves of equal frequency having amplitudes 10 mm, 4 mm and 7 mm arrive at a given point with successive phase difference of \(\pi /2\); the amplitude of the resulting wave in mm given by
- (a)
7
- (b)
6
- (c)
5
- (d)
4