Sound Test

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Sound Test - 68

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Weekly Quiz Competition

Question 1
1 / -0

The time period of the second hand in a clock is :

A
$$1$$ minute

B
$$1$$ hour

C
$$2$$ hours

D
$$24$$ hours

Solution

The seconds hand in a clock completes one full cycle in $$60 \ seconds = 1 \ minute$$

Hence, time period $$T = 1 \ minute$$
Question 2
1 / -0

The minimum distance between the source of the sound and the obstacle for an echo (at $$20^{\circ}\,C$$) to take place is :

A
$$17.2\,m $$

B
$$ 1.72\,m $$

C
$$ 17.8\,m $$

D
$$34.4\,m$$

Solution
Question 3
1 / -0

The time period of a vibrating body is $$ 0.02\,s $$. The frequency of the vibrating body will be

A
$$ 100 \,Hz $$

B
$$ 20 \,Hz $$

C
$$ 50\,Hz $$

D
$$ 1 \,Hz $$

Solution

Given,
Time period vibrating body $$T=0.02\ s$$
Frequency $$f=\dfrac1f=\dfrac{1}{0.02}=50\ s^{-1}$$ or $$50 Hz$$
Question 4
1 / -0

What is the range of wavelengths of audible sound in air? (velocity of sound in air is $$340\ m/s$$)

A
$$\text{0.17 m to 170 m}$$

B
$$\text{0.17 m to 17 m}$$

C
$$\text{0.017 m to 17 m}$$

D
$$\text{0.017 m to 1.7 m}$$

Solution

A person has a hearing range from $$20\ Hz$$ to $$20\ kHz$$.
Let, $$f_1=20\ Hz$$ and $$f_2=20000\ Hz$$
Velocty of sound in air, $$v = 340\ m/s$$
wavelength, $$\lambda$$

We know,
$$ \lambda = \dfrac{v} {f}$$

For frequency, $$f_1=20\ Hz$$
$$ \lambda_1 = \dfrac{v} {f_1}$$

$$ \lambda_1 = \dfrac{340} {20}$$

$$\lambda_1= 17 \space m$$

For frequency, $$f_2=20000\ Hz$$
$$ \lambda_2 = \dfrac{v} {f_2}$$

$$ \lambda_2 = \dfrac{340} {20000}$$

$$\lambda_2= 0.017 \space m$$

The range of wavelengths of audible sound in air is $$0.017\ m$$ to $$17\ m.$$
Question 5
1 / -0

What is the type of sound waves propagating in a solid?

A
Longitudinal only

B
Transverse only

C
It can be either longitudinal or transverse

D
Non-mechanical

Solution

It can be either longitudinal or transverse.
Sound waves propagating in solids can be either longitudinal or transverse. Sound waves as a whole can propagate as transverse or longitude waves in solids due to transfer of energy. Longitudinal waves are waves that have vibrations along the direction of wave propagation. They are also called pressure waves due to the formation of crests and troughs.
Question 6
1 / -0

Which of the following is true for sound wave?

A
$$\lambda \space \alpha \space f^{2}$$

B
$$\lambda \space \alpha \space f$$

C
$$\lambda \space \alpha \space \frac{1} {f}$$

D
$$\lambda \space \alpha \space \frac{1} {f^{2}}$$

Solution

$$\lambda \space \alpha \space \frac{1} {f}$$
Wave velocity = Wavelength $$\times$$ Frequency
So Wavelength= $$\frac{Wave\quad velocity}{Frequency}$$
Thus, we can say that wavelength is inversely proportional to the frequency.
Question 7
1 / -0

A hospital uses an ultrasonic scanner to locate tumors in a tissue. What is the wavelength of the sound in a tissue in which the speed of the sound is $$1.7 \ km/s$$. the operating frequency of the scanner is $$4.2 \ MHz$$. ( $$1 \ MHz= 10^6 \ Hz)$$

A
$$4.05 \times 10^{-4} \ m$$

B
$$9.05 \times 10^{-4} \ m$$

C
$$6.05 \times 10^{-4} \ m$$

D
$$4.05 \times 10^{4} \ m$$

Solution

Given $$ f= 4.2 MHz = 4.2 \times 10^6 Hz$$
Speed $$v= 1.7 km/s= 1.7 \times 10^3 m/s$$
Since $$v= f \lambda \implies \lambda= \dfrac{1.7 \times 10^3}{4.2 \times 10^6}= 4.05 \times 10^{-4} m$$
Question 8
1 / -0

On sending an ultrasonic wave form a ship towards the bottom of a sea, the time interval between sending the wave and receiving it back is found to be 1.5 s. If the velocity of wave in sea water is 1400 $$ms^{-1}$$ find the depth of the sea.

A
1050 m

B
950 m

C
1000 m

D
1150 m

Solution

As the speed of sound in seawater is 1400 m/s in the question, the distance travelled by sound(ultrasonic wave from the ship) in 1.5 seconds is calculated from the formula
$$Distance\ traveled=velocity\ of\ sound\times time\ taken$$.
That is, $$Distance = 1400 m/s\times 1.5 s$$ $$= 2100 m. $$
This is twice the minimum distance between a source of sound (ship) and the reflector (sea bed) as it is reflected sound.
So, the sea bed is at a distance of 1050 m at least from the ship. Therefore, the depth of the sea is 1.05 km.
Question 9
1 / -0

In a string, longitudinal wave

A
can be produced

B
cannot be produced.

C
May or may not be produced, depending on nature of fluid

D
May or may not be produced, depending on nature of cross section of pipe

Solution

We know that longitudanal waves require vibration of particles in direction of wave motion. These waves can be produced on a spring. Now, if the string is elastic, such waves can be produced as particles can vibrate along the length of the string.
Question 10
1 / -0

On a hot, dry summer day a boy is standing between plane parallel vertical cliffs separated by 75 m. He is 30 m away from one of the cliffs. Consider speed of sound in air on that hot day to be 360 m/s. The boy claps loudly and hears its successive echoes. The time in seconds at which he hears the first four echoes are respectively:

A
$$\frac{1}{6},\frac{1}{4},\frac{5}{12},\frac{5}{12}$$

B
$$\frac{1}{6},\frac{1}{4},\frac{7}{12},\frac{2}{3}$$

C
$$\frac{1}{4},\frac{1}{3},\frac{5}{12},\frac{7}{12}$$

D
$$\frac{1}{6},\frac{1}{4},\frac{1}{3},\frac{5}{12}$$

Solution

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Re-Attempt Weekly Quiz Competition

Sound Test - 68

Result

Sound Test - 68

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SHARING IS CARING

Question 1

$$1$$ minute

$$1$$ hour

$$2$$ hours

$$24$$ hours

Solution

Question 2

$$17.2\,m $$

$$ 1.72\,m $$

$$ 17.8\,m $$

$$34.4\,m$$

Solution

Question 3

$$ 100 \,Hz $$

$$ 20 \,Hz $$

$$ 50\,Hz $$

$$ 1 \,Hz $$

Solution

Question 4

$$\text{0.17 m to 170 m}$$

$$\text{0.17 m to 17 m}$$

$$\text{0.017 m to 17 m}$$

$$\text{0.017 m to 1.7 m}$$

Solution

Question 5

Longitudinal only

Transverse only

It can be either longitudinal or transverse

Non-mechanical

Solution

Question 6

$$\lambda \space \alpha \space f^{2}$$

$$\lambda \space \alpha \space f$$

$$\lambda \space \alpha \space \frac{1} {f}$$

$$\lambda \space \alpha \space \frac{1} {f^{2}}$$

Solution

Question 7

$$4.05 \times 10^{-4} \ m$$

$$9.05 \times 10^{-4} \ m$$

$$6.05 \times 10^{-4} \ m$$

$$4.05 \times 10^{4} \ m$$

Solution

Question 8

1050 m

950 m

1000 m

1150 m

Solution

Question 9

can be produced

cannot be produced.

May or may not be produced, depending on nature of fluid

May or may not be produced, depending on nature of cross section of pipe

Solution

Question 10

$$\frac{1}{6},\frac{1}{4},\frac{5}{12},\frac{5}{12}$$

$$\frac{1}{6},\frac{1}{4},\frac{7}{12},\frac{2}{3}$$

$$\frac{1}{4},\frac{1}{3},\frac{5}{12},\frac{7}{12}$$

$$\frac{1}{6},\frac{1}{4},\frac{1}{3},\frac{5}{12}$$

Solution

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