A siren emitting a sound of frequency \(800\) Hz moves away from an observer towards a cliff at a speed of \(15\) ms-1. Then, the frequency of sound that the observer hears in the echo reflected from the cliff is:
(Take, the velocity of sound in air = \(330\) ms-1)
1. \(800\) Hz
2. \(838\) Hz
3. \(885\) Hz
4. \(765\) Hz
A source of sound S emitting waves of frequency 100 Hz and an observer O are located at some distance from each other. The source is moving with a speed of 19.4 ms-1 at an angle of with the source-observer line as shown in the figure. The observer is at rest. The apparent frequency observed by the observer (velocity of sound in air 330 ms-1), is:
1. 100 Hz
2. 103 Hz
3. 106 Hz
4. 97 Hz
A speeding motorcyclist sees a traffic jam ahead of him. He slows down to 36 km/hour. He finds that traffic has eased and a car moving ahead of him at 18 km/hour is honking at a frequency of 1392 Hz. If the speed of sound is 343 m/s, the frequency of the honk as heard by him will be:
1. 1332 Hz
2. 1372 Hz
3. 1412 Hz
4. 1454 Hz
The driver of a car travelling at a speed of 30 m/s towards a hill sounds a horn of frequency 600 Hz. If the velocity of sound in air is 330 m/s, the frequency of reflected sound as heard by the driver is:
1. 550 Hz
2. 555.5 Hz
3. 720 Hz
4. 500 Hz
Two cars moving in opposite directions approach each other at speeds of 22 m/s and 16.5 m/s, respectively. The driver of the first car blows a horn with a frequency of 400 Hz. The frequency heard by the driver of the second car is [assume velocity of sound to be 340 m/s]:
1. 361 Hz
2. 411 Hz
3. 448 Hz
4. 350 Hz
An observer moving at a velocity of 20 m/s is moving away from a source moving at a speed of 10 m/s towards the observer.
If the frequency of the source is 'f', then find the frequency observed by the observer is: ( )
1.
2.
3.
4. f
A train moves towards a stationary observer at a speed of 34 m/s. The train sounds a whistle and its frequency registered is . If the train's speed is reduced to 17 m/s, the frequency registered is . If the speed of sound is 340 m/s , then the ratio is
1.
2.
3. 2
4.
A boy is walking away from a wall towards an observer at a speed of 1 metre/sec and blows a whistle whose frequency is 680 Hz. The number of beats heard by the observer per second is (Velocity of sound in air = 340 metres/sec)
1. Zero
2. 2
3. 8
4. 4
A source and listener
are both moving towards each other at a speed of v/10, 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 :
1. 1.11 f
2. 1.22 f
3. f
4. 1.27 f
The driver of a car traveling at a speed of 30 m/s towards a hill sounds a horn at a frequency of 600 Hz. If the velocity of sound in air is the frequency of reflected sound as heard by the driver is
1. 550 Hz
2. 555.5 Hz
3. 720 Hz
4. 500 Hz