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 source emits a sound of frequency of 400 Hz, but the listener hears it to be 390 Hz. Then 

(1) The listener is moving towards the source

(2) The source is moving towards the listener

(3) The listener is moving away from the source

(4) The listener has a defective ear

Two waves having sinusoidal waveforms have different wavelengths and different amplitudes. They will be having :

(1) Same pitch and different intensity

(2) Same quality and different intensity

(3) Different quality and different intensity

(4) Same quality and different pitch

The ends of a stretched wire of length L are fixed at x = 0 and x = L. In one experiment, the displacement of the wire is $y_1=A\sin (\pi x/L)\sin \omega t$ and energy is E₁, and in another experiment its displacement is $y_2=A\sin (2\pi x/L)\sin 2\omega t$ and energy is E₂. Then :

(1) E₂ = E₁

(2) E₂ = 2E₁

(3) E₂ = 4E₁

(4) E₂ = 16E₁

The difference between the apparent frequency of a source of sound as perceived by an observer during its approach and recession is 2% of the natural frequency of the source. If the velocity of sound in air is 300 m/sec, the velocity of the source is : (It is given that velocity of source << velocity of sound) 

(1) 6 m/sec

(2) 3 m/sec

(3) 1.5 m/sec

(4) 12 m/sec

A police car moving at 22 m/s, chases a motorcyclist. The policeman sounds his horn at 176 Hz, while both of them move towards a stationary siren of frequency 165 Hz. Calculate the speed of the motorcycle, if it is given that he does not observe any beats 

(1) 33 m/s

(2) 22 m/s

(3) Zero

(4) 11 m/s

The equation of displacement of two waves are given as $y_1=10\sin \left(3\pi t+\frac{{\displaystyle \pi }}{{\displaystyle 3}}\right)$; $y_2=5(\sin 3\pi t+\sqrt{3}\cos 3\pi t)$. Then what is the ratio of their amplitudes ?

1. 1 : 2

2. 2 : 1

3. 1 : 1

4. None of these

An organ pipe is closed at one end has a fundamental frequency of 1500 Hz. The maximum number of overtones generated by this pipe which a normal person can hear is : 

(1) 14

(2) 13

(3) 6

(4) 9

The correct graph between the frequency n and square root of density (ρ) of wire, keeping its length, radius and tension constant, is :

(1)

(2)

(3)

(4)