Waves Test

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Waves Test - 35

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Weekly Quiz Competition

Question 1
1 / -0

The velocity of sound in a gas is 4 times that in air at the same temperature. When a tunning fork is sounded in air a wave of frequency 480 and wavelength. $${\lambda}_{1}$$ is produced. The same fork is sounded in the gas and if $${\lambda}_{2}$$ is the wavelength of the wave, then $${{\lambda}_{2}}/{{\lambda}_{1}}$$ is

A
1

B
2

C
4

D
$${1}/{2}$$

Solution
Question 2
1 / -0

The depth of the troughs of a wave is called its

A
amplitude

B
displacement

C
frequency

D
none of these

Solution

the depth of troughs of a wave is max distance a particle can cover from mean position and which is amplitude so the answer is A.
Question 3
1 / -0

Figure shows the shape of a part of a long string in which transverse waves are produced. Which pair of particles are in phase?

A
A and G

B
D and G

C
B and E

D
C and K

Solution

Same phase implies that the wave should have same frequency as well as same wavelength. But there are only two points in the given wave which satisfies the following condition, the point A and G are the wave producers as we can see that wave produced after A and G exactly match each other i.e. they are in phase.
Question 4
1 / -0

A ripple is created in water. The amplitude at a distance of 5 cm from the point where the sound ripple was created is 4 cm. Ignoring damping, what will be the amplitude at the distance of 10 cm.

A
$$\sqrt{16}\, cm$$

B
$$\sqrt{8}\, cm$$

C
$$\sqrt{4}\, cm$$

D
$$\sqrt{2}\, cm$$

Solution

Spherical waves are created in water.
Energy of wave at distance $$r$$ $$E_r \propto \dfrac{1}{r}$$
But $$E_r \propto A_r^2$$
where $$A_r$$ is the amplitude of wave
$$\implies$$ $$A_r \propto \dfrac{1}{\sqrt{r}}$$
Given : $$A_5 = 4$$ cm $$ r_1 = 5$$cm $$r_2 = 10$$cm
$$\implies$$ $$A_{10}=\sqrt{\dfrac{r_1}{r_2}}A_5 = \sqrt{\dfrac{5}{10}}\times 4 = \sqrt{8}$$ cm
Question 5
1 / -0

The frequency of light whose wave length is $$5000{A}^{}$$ is

A
$$15 \times {10}^{13}$$ cycles per second

B
$$5000$$ cycles per second

C
$$6 \times {10}^{14}$$ cycles per second

D
$$15 \times {10}^{16}$$ cycles per second

Solution

We know that for a wave, velocity $$(v)=$$ wavelength $$(\lambda)\times $$ frequency $$(f)$$
Here $$v=3\times 10^8 m/s $$, velocity of light and $$\lambda=5000 A^o=5000\times 10^{-10} m$$
Thus, $$f=\dfrac{3\times 10^8}{5000\times 10^{-10}}=6\times 10^{14} \ Hz$$ or cycles per second.
Question 6
1 / -0

An anchored boat is rocked by waves whose crests are 100 m apart and whose velocity is $$25\:m/s$$. How often do the crests reach the boat?

A
$$0.8 sec$$

B
$$4 sec$$

C
$$75 sec$$

D
$$2500 sec$$

Solution

Given that,

The distance between two consecutive crests is 100 m. This means that the wavelength of the wave is 100 m.

The velocity of the wave = 25 m/s

We have,

$$velocity=\dfrac{wavelength}{time\,period}$$

Therefore,

$$Time \,period=\dfrac{wavelength}{velocity}$$

$$time\,period=\dfrac{100}{25}=4\,sec$$
Question 7
1 / -0

A wave travels at a speed of $$798 m{s}^{-1}$$. If its wavelength is $$3m$$. what is the frequency of the wave? Will it be audible or not?

A
$$2394 Hz$$, inaudible

B
$$266 Hz$$, Audible

C
$$26600 Hz$$, audible

D
$$26600 Hz$$, Inaudible

Solution

$$v = 798 m{s}^{-1}$$, $$\lambda =3m$$
$$v = $$$$\lambda $$$$f$$
$$f=\dfrac {v}{\lambda } = \dfrac {798}{3 }=266 Hz$$
Since audible range of frequency is $$20 Hz$$ to $$20,000 Hz$$. The given frequency will be audible.
Question 8
1 / -0

A loud rattling sound is produced by a car at some particular speed. This phenomenon is due to

A
resonance.

B
natural vibrations

C
defect in the design of the car.

D
None of the above

Solution
Question 9
1 / -0

A boat at anchor is rocked by waves whose crests are $$100\ m$$ apart and velocity is $$25 \ m/sec$$. The boat bounces up once in every :

A
$$2500s$$

B
$$75s$$

C
$$4s$$

D
$$0.25s$$

Solution

Information provided:
Wavelength = 100m
Wave velocity = 25m/s
Wave velocity = Frequency x wavelength
$$v=f\lambda $$
Frequency = 25/100
Time period = 100/25 = 4 sec
Question 10
1 / -0

A sound wave is a pressure wave; regions of high (compressions) and low pressure (rarefactions) are established as the result of the vibrations of the sound source. These compressions and rarefactions result because sound:

A
is more dense than air and thus has more inertia, causing the bunching up of sound.

B
waves have a speed which is dependent only upon the properties of the medium.

C
is like all waves; it is able to bend into the regions of space behind obstacles.

D
is able to reflect off fixed ends and interfere with incident wavesvibrates longitudinally; the longitudinal movement of air produces pressure fluctuations.

Solution

These compressions and rarefactions result because sound is able to reflect off fixed ends and interfere with incident wave vibrates longitudinally; the longitudinal movement of air produces pressure fluctuations.
Compressions are the regions of high density and rarefactions are regions of low density.

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Waves Test - 35

Result

Waves Test - 35

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SHARING IS CARING

Question 1

1

2

4

$${1}/{2}$$

Solution

Question 2

amplitude

displacement

frequency

none of these

Solution

Question 3

A and G

D and G

B and E

C and K

Solution

Question 4

$$\sqrt{16}\, cm$$

$$\sqrt{8}\, cm$$

$$\sqrt{4}\, cm$$

$$\sqrt{2}\, cm$$

Solution

Question 5

$$15 \times {10}^{13}$$ cycles per second

$$5000$$ cycles per second

$$6 \times {10}^{14}$$ cycles per second

$$15 \times {10}^{16}$$ cycles per second

Solution

Question 6

$$0.8 sec$$

$$4 sec$$

$$75 sec$$

$$2500 sec$$

Solution

Question 7

$$2394 Hz$$, inaudible

$$266 Hz$$, Audible

$$26600 Hz$$, audible

$$26600 Hz$$, Inaudible

Solution

Question 8

resonance.

natural vibrations

defect in the design of the car.

None of the above

Solution

Question 9

$$2500s$$

$$75s$$

$$4s$$

$$0.25s$$

Solution

Question 10

is more dense than air and thus has more inertia, causing the bunching up of sound.

waves have a speed which is dependent only upon the properties of the medium.

is like all waves; it is able to bend into the regions of space behind obstacles.

is able to reflect off fixed ends and interfere with incident wavesvibrates longitudinally; the longitudinal movement of air produces pressure fluctuations.

Solution

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