Waves Test

Result

Waves Test - 68

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Weekly Quiz Competition

Question 1
4 / -1

An observer moves towards a stationary source of sound, with a velocity one-fifth of the velocity of sound. What is the percentage increase in the apparent frequency?

A
5%

B
20%

C
Zero

D
0.5%

Solution
Question 2
4 / -1

The apparent frequency of a note, when a listener moves towards a stationary source, with velocity of 40 m/s is 200 Hz. When he moves away from the same source with the same speed, the apparent frequency of the same note is 160 Hz. The velocity of sound in air is (in m/s

A
360

B
330

C
320

D
340

Solution
Question 3
4 / -1

A source of sound of frequency 256 Hz is moving rapidly towards a wall with a velocity of 5m/s. The speed of sound is 330 m/s. If the observer is between the wall and the source, then beats per second heard will be

A
7.8 Hz

B
7.7 Hz

C
3.9 Hz

D
Zero

Solution
Question 4
4 / -1

A man sitting in a moving train hears the whistle of the engine. The frequency of the whistle is 600 Hz

A
The apparent frequency as heard by him is smaller than 600 Hz

B
The apparent frequency is larger than 600 Hz

C
The frequency as heard by him is 600 Hz

D
None of the above
Question 5
4 / -1

A whistle of frequency 500 Hz tied to the end of a string of length 1.2 m revolves at 400 rev/min. A listener standing some distance away in the plane of rotation of whistle hears frequencies in the range (speed of sound = 340 m/s)

A
436 to 586

B
426 to 574

C
426 to 584

D
436 to 674

Solution
Question 6
4 / -1

A train moves towards a stationary observer with speed 34 m/s. The train sounds a whistle and its frequency registered by the observer is f₁. If the train\'s speed is reduced to 17 m/s, the frequency registered is f₂ . If the speed of sound is 340 m/s then the ratio f₁ / f₂ is

A
18/19

B
1/2

C
2

D
19/18

Solution
Question 7
4 / -1

If source and observer both are relatively at rest and if speed of sound is increased then frequency heard by observer will

A
Increases

B
Decreases

C
Cannot be predicted

D
Will not change
Question 8
4 / -1

A siren placed at a railway platform is emitting sound of frequency 5 kHz. A passenger sitting in a moving train A records a frequency of 5.5 kHz while the train approaches the siren. During his return journey in a different train B he records a frequency of 6.0 kHz while approaching the same siren. The ratio of the velocity of train B to that of train A is

A
242/252

B
2

C
5/6

D
11/6

Solution
Question 9
4 / -1

A car sounding a horn of frequency 1000 Hz passes an observer. The ratio of frequencies of the horn noted by the observer before and after passing of the car is 11 : 9. If the speed of sound is v, the speed of the car is

A

B

C

D

Solution
Question 10
4 / -1

A bus is moving with a velocity of 5 m/s towards a huge wall. The driver sounds a horn of frequency 165 Hz. If the speed of sound in air is 355 m/s, the number of beats heard per second by a passenger on the bus will be

A
6

B
5

C
3

D
4

Solution