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 : 

(1) 10/9

(2) 11/10

(3) (11/10)²

(4) (9/10)²

The speed of sound in air at a given temperature is 350 m/s. An engine blows whistle at a frequency of 1200 cps. It is approaching the observer with velocity 50 m/s. The apparent frequency in cps heard by the observer will be :

(1) 600

(2) 1050

(3) 1400

(4) 2400

The Doppler's effect is applicable for :

(1) Light waves

(2) Sound waves

(3) Space waves

(4) Both (1) and (2)

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

(1) 9 : 8

(2) 8 : 9

(3) 1 : 1

(4) 9 : 10

(Speed of sound v = 340 m/s)

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 motor car blowing a horn of frequency 124vib/sec moves with a velocity 72 km/hr towards a tall wall. The frequency of the reflected sound heard by the driver will be (velocity of sound in air is 330 m/s) 

(1) 109 vib/sec

(2) 132 vib/sec

(3) 140 vib/sec

(4) 248 vib/sec

A source of sound of frequency n is moving towards a stationary observer with a speed S. If the speed of sound in air is V and the frequency heard by the observer is n₁, the value of n₁/n is 

(1) (V + S)/V

(2) V/(V + S)

(3) (V – S)/V

(4) V/(V – S)

An observer is moving away from the source of the sound of frequency 100 Hz. His speed is 33 m/s. If the speed of sound is 330 m/s, then the observed frequency is :

(1) 90 Hz

(2) 100 Hz

(3) 91 Hz

(4) 110 Hz

An observer standing at the station observes frequency 219 Hz when a train approaches and 184 Hz when train goes away from him. If velocity of sound in air is 340 m/s, then velocity of train and actual frequency of whistle will be 

(1) $15.5m{s}^{-1},200Hz$

(2) $19.5m{s}^{-1},205Hz$

(3) $29.5m{s}^{-1},200Hz$

(4) $32.5m{s}^{-1},205Hz$

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