A siren emitting sound of frequency 500 Hz is going away from a static listener with a speed of 50 m/sec. The frequency of sound to be heard, directly from the siren, is :

(1) 434.2 Hz

(2) 589.3 Hz

(3) 481.2 Hz

(4) 286.5 Hz

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

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

2. The apparent frequency is larger than 600 Hz

3. The frequency as heard by him is 600 Hz

4. None of the above

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) 

(1) 436 to 586

(2) 426 to 574

(3) 426 to 584

(4) 436 to 674

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 

(1) 18/19

(2) 1/2

(3) 2

(4) 19/18

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

(1) Increases

(2) Decreases

(3) Can not be predicted

(4) Will not change

A source and an observer move away from each other with a velocity of 10 m/s with respect to ground. If the observer finds the frequency of sound coming from the source as 1950 Hz, then actual frequency of the source is (velocity of sound in air = 340 m/s) 

(1) 1950 Hz

(2) 2068 Hz

(3) 2132 Hz

(4) 2486 Hz

A whistle revolves in a circle with an angular speed of 20 rad/sec using a string of length 50 cm. If the frequency of sound from the whistle is 385 Hz, then what is the minimum frequency heard by an observer, which is far away from the centre in the same plane ? $(v_{sound} = 340 m/s)$

(1) 333 Hz

(2) 374 Hz

(3) 385 Hz

(4) 394 Hz

A Siren emitting sound of frequency 800 Hz is going away from a static listener with a speed of 30 m/s, frequency of the sound to be heard by the listener is (take velocity of sound as 330 m/s)

(1) 733.3 Hz

(2) 644.8 Hz

(3) 481.2 Hz

(4) 286.5 Hz

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 the passing of the car is 11 : 9. If the speed of sound is v, the speed of the car is 

(1) $\frac{1}{10}v$

(2) $\frac{1}{2}v$

(3) $\frac{1}{5}v$

(4) v

A small source of sound moves on a circle as shown in the figure and an observer is standing on O. Let n₁, n₂ and n₃ be the frequencies heard when the source is at A, B, and C respectively. Then

(1) n₁ > n₂ > n₃

(2) n₂ > n₃ > n₁

(3) n₁ = n₂ > n₃

(4) n₂ > n₁ > n₃