Waves And Sound Test

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Waves And Sound Test - 3

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Question 1
1 / -0

If at a place, the speed of a sound wave of frequency 300 Hz is v, then the speed of another wave of frequency 150 Hz at the same place is

A
v

B
v/2

C
2v

D
4v

Solution

The relation for speed is

Here, v is speed.
is frequency.
is wavelength.
If a 300 Hz frequency wave has a speed v, then a 150 Hz frequency wave also has a speed v because speed is constant through a particular medium. Only the frequency and wavelength vary.
Question 2
1 / -0

Bells are made of metal and not of wood, because

A
thermal conductivity of metal is greater than that of wood

B
density of the metal is greater than that of wood

C
sound is not conducted by metals, but is radiated

D
wood dampens vibration while metals are elastic

Solution

Bells are made of metal and not of wood because metals are elastic and wood dampens vibrations. On the contrary, metals do not dampen the vibrations.
Question 3
1 / -0

Ultrasonic, infrasonic and audible waves travel through a medium with speeds v_u, v_i and v_a,respectively. Which of the following relations holds true?

A
v_i = v_a = v_u

B
v_u > v_a > v_i

C
v_u < v_a < v_i

D
v_a ≤ v_u≤ v_i

Solution

All the three waves will travel with the same speed. The difference lies in their wavelengths and frequencies.
Question 4
1 / -0

If the intensity ratio of two waves is 4 : 1, then the ratio of their amplitudes is

A
2 : 1

B
1 : 2

C
4 : 1

D
1 : 4

Solution

Intensity is directly proportional to the square of amplitude of a wave.
So, I = kA²

A₁: A₂= 2 : 1
Question 5
1 / -0

For each degree centigrade rise of temperature, the velocity of sound in air increases by

A
0.61 m/sec

B
0.61 cm/sec

C
0.61 km/sec

D
0.61 ft/sec

Solution
Question 6
1 / -0

A string A has double the length, double the tension, double the diameter and double the density than string B. The ratio of their fundamental frequencies of vibration (n_A and n_B) is

A

B

C
2

D
4

Solution

For string B,
Length = l, Tension = T, Diameter = d, Density =

m =

n_B =

=

For string A,

Their ratio = 1 : 4
Question 7
1 / -0

The speed of sound is maximum in

A
water

B
steel

C
vacuum

D
air

Solution

Speed of sound is maximum in steel.
Question 8
1 / -0

Transverse waves are generated in uniform steel wires A and B by attaching their free ends to a vibrating source of frequency 500 Hz. The diameter of wire A is half that of wire B and the tension of wire A is half that of wire B. The velocities of waves in wire A and wire B are in the ratio

A
1 : 2

B
2 : 1

C
1 :

D
: 1

Solution
Question 9
1 / -0

Velocity of sound in a gas is proportional to

A
square root of isothermal elasticity

B
adiabatic elasticity

C
square root of adiabatic elasticity

D
isothermal elasticity

Solution

The velocity of sound in gas is proportional to the square root of adiabatic elasticity.
The formula is,
V =, where K is the elasticity
Question 10
1 / -0

The velocity of sound in air is not affected by changes in

A
moisture contents of the air

B
temperature of the air

C
atmospheric pressure

D
composition of air

Solution

The velocity of sound in air is not affected by the changes in atmospheric pressure.
Speed of sound C =
P - Static air pressure
- Density of air (Both are proportional at same temperature)
The ratio is always constant on a high mountain or even on sea level altitude. The speed of sound varies with height only because of changes in temperature.
Question 11
1 / -0

Which of the following statements is correct?

A
Changes in air temperature have no effect on the speed of sound.

B
Changes in air pressure have no effect on the speed of sound.

C
The speed of sound in water is lower than that in air.

D
The speed of sound does not depend on the frequency of the source.

Solution

The speed of sound does not depend on the frequency of the source.
It just depends on the medium of travel.
Hence, option 4 is the correct answer.
Question 12
1 / -0

The speed of a sound wave having a frequency 256 Hz compared with the speed of a sound wave having a frequency 512 Hz is

A
half as great

B
the same

C
twice as great

D
four times as great

Solution

The relation is:

V = f.

Here, V is speed, f is frequency and is wavelength.

As f changes, also changes accordingly, making the V same.

Hence, both the frequencies will have the same speed.
Question 13
1 / -0

The loudness of sound depends upon

A
amplitude

B
pitch

C
velocity

D
wavelength

Solution

The loudness of sound depends on the amplitude.
Question 14
1 / -0

The shrillness (pitch) of a sound note depends upon

A
amplitude

B
frequency

C
wavelength

D
velocity

Solution

The shrillness (pitch) of a sound note depends upon frequency. The greater is the frequency, the greater will be the shrillness.
Question 15
1 / -0

The sound of a lion is different from that of a mosquito because

A
both the animals have different sizes

B
both the sounds travel with different velocities

C
both the sounds have different pitches

D
both the sounds have different phases

Solution

Roaring of a lion produces a sound of low pitch and high intensity/loudness, whereas the buzzing of a mosquito produces a sound of high pitch and low intensity/loudness. This is how the roar of a lion can be differentiated from the buzzing of a mosquito.
Question 16
1 / -0

The quality of a tone

A
decreases with loudness

B
varies directly as pitch

C
depends on the overtones that are present there

D
varies inversely as frequency

Solution

The quality of a tone depends upon the overtones that are present there.
Question 17
1 / -0

It is possible to recognize a person by hearing his voice even if he is hidden behind a solid wall. This is due to the fact that his voice

A
has a definite pitch

B
has a definite quality

C
has a definite loudness

D
can penetrate the wall

Solution

He can be recognized because his voice has a definite quality.
Question 18
1 / -0

The same note being played on a Sitar and a Veena differs in

A
only pitch

B
both pitch and quality

C
only quality

D
neither pitch nor quality

Solution

The same note played on sitar and veena differ in their quality, i.e. the number of harmonics present, their order and relatives intensities.
Sitar is an instrument that comes under Hindustani classical instruments which is usually the music style in North India. While, Veena comes under Carnatic music style of instruments which is usually the music style in South India.
Veena is low pitched used for singing, while sitar is high pitched. Singing along with sitar is not easy, while it is easier to sing with a veena.
Question 19
1 / -0

In an orchestra, the musical sounds of different instruments are distinguished from one another on the basis of

A
pitch

B
loudness

C
quality

D
overtones

Solution

In an orchestra, the musical sounds of different instruments are distinguished from one another on the basis of quality.
Question 20
1 / -0

Two identical strings are stretched at tensions T_A and T_B. A tuning fork is used to set them in vibration. If A vibrates in its fundamental mode and B in its second harmonic mode, which of the following relations holds true?

A
T_A = 2T_B

B
T_A= 4T_B

C
2T_A = T_B

D
4T_A = T_B

Solution

Let n be the frequency of the tuning fork, be the length of each string and m be the mass per unit length of each string.

So, n =

=

Or
or T_A = 4T_B