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
Sound waves cannot be
- (a)
refracted
- (b)
polarised
- (c)
scattered
- (d)
used to produce hologram
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
One of the similarities between sound and light is that both
- (a)
are transverse waves
- (b)
can show holographic effects
- (c)
can pass through vacuum
- (d)
travel with constant speed in free space
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
A train moving away from a cliff whistles when at a distance of 300 m from it an echo is heard by the driver in 2s. The speed of the train in km h-1 is
- (a)
30
- (b)
108
- (c)
648
- (d)
660
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 velocity of sound in carbon dioxide is less than in hydrogen because
- (a)
carbon dioxide has more degrees of freedom
- (b)
carbon dioxide is soluble in water
- (c)
carbon dioxide is heavier than hydrogen
- (d)
carbon dioxide is a compound and hydrogen is an element
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
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
A sonometer of fixed length is to produce one octave lower than before by varying the tension. The fractional change in tension required for this purpose will be
- (a)
1/4
- (b)
3/4
- (c)
1/2
- (d)
3/4
A tuning fork is an octave to an organ pipe. It can sound only with
- (a)
a closed pipe
- (b)
an open pipe
- (c)
both open and closed pipes
- (d)
NONE OF THE ABOVE
Consider the following statement :
A. The frequency range detected by the eye has a range factor of about 2.
B. The human ear has a range factor of about 1000
C. The frequency of waves due to vibrations in solid atoms can be as high as that os visible light
Choose if
- (a)
A is correct
- (b)
B is correct
- (c)
C is correct
- (d)
A, B, C are correct
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 thin aluminium rod (diameter = 1 mm) is very long and is under a uniform tension of 1000 N. Its Young's modulus (Y) is 7.0 X 1010 Pa and its density \((\rho )\) is 2.70 g cm-3. The velocity of transverse waves on the rod is
- (a)
5092 ms-1
- (b)
equal to that longitudinal waves and it is 5092 ms-1
- (c)
686.7 ms-1 and it is also that of longitudinal waves
- (d)
68607 ms-1
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
By using special laboratory apparataus, it is possible to produce sound waves with wavelength in air as small as, comparable with wavelength of
- (a)
infrared light
- (b)
visible light
- (c)
ultraviolet light
- (d)
x-rays
An observer rides with a moving sound source directly toward a large vertical wall. The vehicle has a constant speed of 36 km per hour and the source has a frequency of 100 Hz. As a result of the combination of the direct and reflected sounds the observer hears beats at a frequency of
[velocity of sound = 360 ms-1]
- (a)
5.7 Hz
- (b)
15.7 Hz
- (c)
22.5 Hz
- (d)
3.5 Hz
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
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
In stationary wave the strain is
- (a)
maximum at nodes
- (b)
maximum at antinodes
- (c)
constant throughout
- (d)
NONE OF THE ABOVE
A sound wave travelling with a velocity V in a medium reaches a point on the interface of medium A and medium B. If the velocity in the medium B be 2V, then the angle of incidence for total internal reflection of the wave will be greater than
- (a)
\({ 15 }^{ \circ }\)
- (b)
\({ 30 }^{ \circ }\)
- (c)
\({ 45 }^{ \circ }\)
- (d)
\({ 90 }^{ \circ }\)
If n1, n2 and n3 are the fundamental frequencies of three segments into which a string is divided, then the original fundamental frequency n of the string is given by
- (a)
\(\frac { 1 }{ n } =\frac { 1 }{ { n }_{ 1 } } +\frac { 1 }{ { n }_{ 2 } } +\frac { 1 }{ { n }_{ 3 } } \)
- (b)
\(\frac { 1 }{ \sqrt { n } } =\frac { 1 }{ \sqrt { { n }_{ 1 } } } +\frac { 1 }{ \sqrt { { n }_{ 2 } } } +\frac { 1 }{ \sqrt { { n }_{ 3 } } } \)
- (c)
\(\sqrt { n } =\sqrt { { n }_{ 1 } } +\sqrt { { n }_{ 2 } } +\sqrt { { n }_{ 3 } } \)
- (d)
\(n={ n }_{ 1 }+{ n }_{ 2 }+{ n }_{ 3 }\)
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