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

1. 750 Hz

2. 857 Hz

3. 1143 Hz

4. 1333 Hz

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

A bat is flitting about in a cave, navigating via ultrasonic beeps. Assume that the sound emission frequency of the bat is 40 kHz. During one fast swoop directly toward a flat wall surface, the bat moves at 0.03 times the speed of sound in the air. What frequency does the bat hear reflected off the wall?

1. 41.27 kHz

2. 42.67 kHz

3. 41.23 kHz

4. 42.47 kHz

A source of sound moves away with the velocity of sound from a stationary observer. The frequency of the sound heard by the observer:

1. remains the same

2. is doubled

3. is halved

4. becomes infinity
 

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: ( $v_{sound}<mspace\; width="1em"></mspace>=<mspace\; width="1em"></mspace>330<mspace\; width="1em"></mspace>m/s$ )

1. $\frac{32}{31}f$

2. $\frac{47}{23}f$

3. $\frac{31}{32}f$

4. f

A SONAR system fixed in a submarine operates at a frequency 40.0 kHz. An enemy submarine moves towards the SONAR with a speed of 360 km/h. What is the frequency of sound reflected by the enemy submarine? (the speed of sound in water to be 1450 m/sec.)

(1) 44.2 kHz

(2) 45.9 kHz

(3) 43.7 kHz

(4) 46.1 kHz

Two cars moving in opposite directions approach each other with speed of 22m/s and 16.5 m/s respectively. The driver of the first car blows a horn having a frequency 400 Hz. The frequency heard by the driver of the second car is [velocity of sound 340m/s]

1. 350Hz

2. 361Hz

3. 411Hz

4. 448Hz

A source of sound moves towards an observer.

1. The frequency of the source is increased

2. The velocity of sound in the medium is increased

3 The wavelength of sound in the medium towards the observer is decreased

4. The amplitude of vibration of the particles is increased

A train moves towards a stationary observer at 50 m/s. The train sounds a whistle and its frequency is registered by the observer as ${\mathrm{f}}_1$. If the train's speed is increased by 25 m/s, the frequency registered is ${\mathrm{f}}_2$. If the speed of sound is 300 m/s, then ${\mathrm{f}}_1$:${\mathrm{f}}_2$ is:

1. 3:5

2. 5:7

3. 7:9

4. 9:10

The change in frequency due to Doppler effect does not depend on

1. the speed of the source

2. the speed of the observer

3. the frequency of the source

4. separation between the source and the observer