# Sound Worksheet-2

Sound Worksheet-2

1. If 25 sound waves are produced per second, what is the frequency in hertz?

A. 25 hertz                                      B. 50 hertz

C. 75 hertz                                      D. 1/25 hertz

1. What is the frequency of a sound wave whose time-period is 0.05 s ?

A. 1/20 hertz     B. 40 hertz        C. 10 hertz         D. 20 hertz

1. The wavelength of sound emitted by a source is 1.7 × 10–2 m. Calculate frequency of the sound, if its velocity is 343.4 m s–1.

A. 2.02 × 102 hertz                       B. 1 × 104 hertz

C. 2.02 × 103 hertz                       D. 2.02 × 104 hertz

1. Sound waves travel with a speed of about 330 m/s. What is the wavelength of sound whose frequency is 550 hertz?

A. 0.6 meter                                  B. 1.6 meter

C. 1 meter                                       D. 1.67 meter

1. A source is producing 1500 sound waves in 3 seconds. If the distance covered by a compression and an adjacent rarefaction be 68 cm. Find velocity, of the sound wave.

A. 340 km/h     B. 340 m/h       C. 340 m/s        D. 340 km/s

1. If a thunder is heard by a man 4 seconds after the lightning is seen, how far is the lightning from the man? (Speed of sound in air = 330 m/s).

A. 82.5 meters                              B. 1320 meters

C. 132 meters                                D. 1200 meters

1. A man claps his hands near a mountain and hears the echo after 4 seconds. If the speed of sound under these conditions be 330 m/s, calculate the distance of the mountain from the man.

A. 660 meters                               B. 1320 meters

C. 330 meters                               D. 165 meters

1. A sonar device attached to a ship sends ultrasonic waves in the sea. These waves are reflected from the bottom of the sea. If the ultrasonic waves take 4 seconds to travel from the ship to the bottom of the sea and back to the ship (in the form of an echo), what is the depth of the sea ? (Speed of sound in water = 1500 m/s).

A. 6000 m         B. 1500 m         C. 3000 m         D. 2000 m

1. Which of the following statement best describes frequency?

A. the maximum disturbance caused by a wave

B. the number of complete vibrations per second

C. the distance between one crest of a wave and the next one

D. the distance traveled by a wave per second

1. Which of the following vibrates when a musical note is produced by the cymbals in an orchestra?

A. stretched strings                      B. stretched membranes

C. metal plates                              D. air columns

1. A

Explanation: The frequency in hertz is equal to the number of waves produced per second.

Since 25 waves are being produced per second, so the frequency of the sound waves is 25 hertz (which is also written as 25 Hz).

1. D

Explanation: The relationship between the frequency and time-period of a wave is :

f = (1/T)

Frequency, f = ?

Time-period, T = 0.05 s

f = (1/0.05)

f = (100/5)

f = 20 Hz

Thus, the frequency of the sound wave is 20 hertz.

1. D

Explanation: The relationship between velocity, frequency and wavelength of a wave is given by the formula:

Velocity, v = 343.4  m s–1

Frequency, f = ?

Wavelength, λ = 1.7 × 10–2 m

V = f × λ

343.4 = f × 1.7 × 10–2

f = 2.02 × 104 Hz

Thus, the frequency of sound is 2.02 × 104 hertz.

1. A

Explanation:

Given:

Speed of waves, v = 330 m/s

Frequency of waves, f = 550 Hz

Wavelength, λ = ?

v = f × λ

So,    330 = 550 × λ

λ = 0.6m

Thus, the wavelength of sound waves is 0.6 meter.

1. C

Explanation:

(a) Frequency. The frequency of a wave is the number of waves produced in 1 second.

No. of waves produced in 3 seconds =1500

So, No. of waves produced in 1 second = (1500/3)

So, the frequency of this sound wave is 500 hertz.

(b) Wavelength. The wavelength (λ) of this sound wave is 68 cm.

(c) Velocity. The formula for calculating the velocity of a sound wave is :

Here, Frequency = 500 Hz

And,  Wavelength, λ = 68 cm

= (68/100) m = 0.68 m

V = f × λ

v = 500 × 0.68 = 340 m/s

Thus, the velocity (or speed) of the sound waves is 340 m/s.

1. B

Explanation: Light travels at a great speed as compared to that of sound, therefore, the flash of light of lightning' will reach the man in no time but sound takes 4 seconds to reach the man. Now :

Speed of sound = 330 m/s

Distance =?

and   Time  = 4 s

Speed = distance/ time

and, Distance = 330 × 4 m = 1320 m

Hence the Lightning is at a distance of 1320 meters from the man.

1. A

Explanation: In this case the time taken by the sound to go from the man to the mountain, and return to the man is 4 seconds. But the time taken by the sound to go from the man to the mountain only will be half of this time, which is (4/2) = 2 seconds.

Speed = distance travelled / time taken

So, 330 = distance travelled  / 2

And, Distance traveled = 330 × 2 metres = 660 meters

Since sound travels a distance of 660 meters in going from the man to the mountain, so the distance of mountain from the man is 660 meters.

1. C

Explanation: The time taken by the ultrasonic sound waves to travel from the ship to the sea-bed, and back to the ship is 4 seconds. So, the time taken by the ultrasonic sound to travel from the ship to sea-bed will be half of this time, which is (4/2) = 2 seconds.

Now, Speed = distance/time

So, 1500 = (distance / 2) = 3000 m

Thus, the depth of this sea below the ship is 3000 metres.

1. B

1. C