Sound Test

Result

Sound Test - 72

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Weekly Quiz Competition

Question 1
1 / -0

The wavelength of sound from a tuning fork of frequency 330 Hz is nearly. Use speed of sound in air as 330 m/s

A
100 cm

B
1000 cm

C
10 cm

D
330 cm

Solution
Question 2
1 / -0

A person has the audible range from $$20 Hz$$ to $$20\times 10^3Hz$$. Find the wavelength range corresponding to these frequencies. Take velocity sound as $$340m/s$$

A
$$15\times 10^{-3}m$$

B
$$11\times 10^{-3}m$$

C
$$17\times 10^{-3}m$$

D
$$15\times 10^{-8}m$$

Solution
Question 3
1 / -0

A person can hear a sound of maximum frequency $$20,000 Hz$$, If the speed of sound in air is 344 $$ms^{-1}$$ the wavelength is :

A
$$0.176 m$$

B
$$0.178 m$$

C
$$0.0172 m$$

D
$$0.0176 m$$

Solution
Question 4
1 / -0

An echo is returned in $$3\ s$$. If the speed of sound is $$342\ m/s$$, then the distance between the source of sound and the reflecting body is:

A
$$513\ m$$

B
$$351\ m$$

C
$$153\ m$$

D
$$254\ m$$

Solution
Question 5
1 / -0

An echo is heard only, if the sound after reflection should reach the ear after:

A
less than $$\frac { 1 }{ 100 } $$s

B
less than $$\frac { 1 }{ 10 } $$s

C
more than $$\frac { 1 }{ 10 } $$s

D
none of these

Solution

A human ear cannot sense every reflection of sound or echo. For the echo to be heard by a human ear, the sound from the source must reach back to source after reflection after more than 0.1 seconds , that is , more than $$1/10s$$.
This is due to the fact that a human ear can not differentiate between source sound and echo sound which are produced less than $$1/10s$$ apart.
Question 6
1 / -0

A person can hear a sound of maximum frequency 20,000 Hz. If the speed of sound in air is 344 $${ ms }^{ -1 },$$ the wavelength of this maximum frequency sound is :

A
0.176 m

B
0.178 m

C
0.0172

D
0.0176 m

Solution
Question 7
1 / -0

A sound signal is simultaneously sent in air and water from a boat on a river. The echo of sound sent back by the river bed is heard in $$4s$$, while the echo sent back by the aeroplane is heard in $$8s$$. Find the distance between aeroplane and river bed.
[velocity of sound in air $$= 350 m/s$$, velocity of sound in water $$= 1500m/s$$]

A
$$4.4km$$

B
$$6.4km$$

C
$$8.8km$$

D
$$13.4km$$

Solution

The sound has to travel twice the distance to give an echo.

Time taken to hear an echo produced by the river bed is $$4\ sec$$.
Distance travelled by the sound in $$4\ sec$$ is $$v_{water}\times t=1500\times4=6000\ m$$
If $$d_{river}$$ is the depth of the river then $$2d_{river}=6000\ m$$
$$\therefore d_{river}=\dfrac{6000}{2}=3000\ m$$

Time taken to hear an echo produced by the aeroplane is $$8\ sec$$.
Distance travelled by the sound in $$8\ sec$$ is $$v_{air}\times t=350\times8=2800\ m$$
If $$d_{aero}$$ is the height of the aeroplane then $$2d_{aero}=2800\ m$$
$$\therefore d_{aero}=\dfrac{2800}{2}=1400\ m$$

Thus, the distance between the river bed and the aeroplane is $$ (3000 + 1400)m= 4400 m= 4.4km$$
Question 8
1 / -0

A stone is dropped in a well which is 19.6m deep. Echo sound is heard after 2.06 sec (after dropping) then the velocity of sound is

A
332.6 m/sec

B
326.7 m/sec

C
300.4 m/sec

D
290.5 m/sec

Solution
Question 9
1 / -0

The echo of a gunshot is heard after $$5\ s$$. Find the distance of the obstacle. Speed of sound is $$320\ m{s^{ - 1}}.$$

A
$$1000\ m$$

B
$$500\ m$$

C
$$800\ m$$

D
$$600\ m$$

Solution

Suppose $$'x'$$ is the distance between shooter and reflecting surface.
For echo to be heard, sound travels distance $$'2x'$$.
So speed of the sound is-
$$V = \dfrac{ 2x }{ t }$$
$$\Rightarrow x = \dfrac{ vt }{ 2 }$$
$$\Rightarrow x = \dfrac{ 320 \times 5 }{ 2 }$$
$$\Rightarrow x = 800\ m$$
Question 10
1 / -0

A man fires a gun and hears the echo after $$2\,\frac{1}{2}sec$$. If the velocity of sound in air is $$340ms^{-1}$$ his distance from the cliff causing the echo is

A
$$2\,\frac{1}{2}km$$

B
$$425m$$

C
$$850m$$

D
$$136m$$