Waves Test

Result

Waves Test - 90

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Weekly Quiz Competition

Question 1
4 / -1

A source of sound emitting a note of frequency 200 Hz moves towards an observer with a velocity v equal to the velocity of sound. If the observer also moves away from the source with the same velocity v, the apparent frequency heard by the observer is

A
50 Hz

B
100 Hz

C
150 Hz

D
200 Hz
Question 2
4 / -1

Two sources A and B are sending notes of frequency 680 Hz. A listener moves from A and B with a constant velocity u. If the speed of sound in air is 340 ms^–1, what must be the value of u so that he hears 10 beats per second?

A
2.0 ms^–1

B
2.5 ms^–1

C
3.0 ms^–1

D
3.5 ms^–1

Solution
Question 3
4 / -1

A source of sound is travelling towards a stationary observer. The frequency of sound heard by the observer is of three times the original frequency. The velocity of sound is v m/sec. The speed of source will be

A

B

C

D

Solution
Question 4
4 / -1

A sound source is moving towards a stationary observer with 1/10 of the speed of sound. The ratio of apparent to real frequency is

A
10/9

B
11/10

C
(11/10)²

D
(9/10)²

Solution
Question 5
4 / -1

Two trains, each moving with a velocity of 30 ms^–1 , cross each other. One of the train gives a whistle whose frequency is 600 Hz. If the speed of sound is 330 ms^–1, the apparent frequency for passengers sitting in the other train before crossing would be

A
600 Hz

B
630 Hz

C
920 Hz

D
720 Hz

Solution
Question 6
4 / -1

Suppose that the speed of sound in air at a given temperature is 400 m/sec. An engine blows a whistle at 1200 Hz frequency. It is approaching an observer at the speed of 100 m/sec. What is the apparent frequency as heard by the observer?

A
600 Hz

B
1200 Hz

C
1500 Hz

D
1600 Hz

Solution
Question 7
4 / -1

The Doppler\'s effect is applicable for

A
Light waves

B
Sound waves

C
Space waves

D
Both (a) and (b)
Question 8
4 / -1

A source of sound is moving with constant velocity of 20 m/s emitting a note of frequency 1000 Hz . The ratio of frequencies observed by a stationary observer while the source is approaching him and after it crosses him will be (Speed of sound v = 340 m/s)

A
9 : 8

B
8 : 9

C
1 : 1

D
9 : 10

Solution
Question 9
4 / -1

A source of sound S is moving with a velocity 50 m/s towards a stationary observer. The observer measures the frequency of the source as 1000 Hz. What will be the apparent frequency of the source when it is moving away from the observer after crossing him? The velocity of sound in the medium is 350 m/s

A
750 Hz

B
857 Hz

C
1143 Hz

D
1333 Hz

Solution
Question 10
4 / -1

A source and listener are both moving towards each other with speed v/100 where v is the speed of sound. If the frequency of the note emitted by the source is f, the frequency heard by the listener would be nearly

A
1.11f

B
1.22f

C
f

D
1.27f

Solution