# Physics test on Waves and Sound

1333 Hz

1143 Hz

857 Hz

750 Hz

A table is revolving on its axis at 5 revolutions per second. A sound source of frequency 1000 Hz is fixed on the table at 70 cm from the axis. The minimum frequency heard by a listener standing at a distance from the table is (speed of sound = 352 m/s) ____.

352 Hz

941 Hz

1066 Hz

1000 Hz

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 , the value of is ____.

A vehicle with a horn of frequency n is moving with a velocity of 30 m/s in a direction perpendicular to the straight line joining the observer and the vehicle. The observer perceives the sound to have a frequency . Then (if the sound velocity in air is 300 m/s) ____.

A whistle giving out 450 Hz approaches a stationary observer at a speed of 33 m/s. The frequency heard by the observer in Hz is ____.

500

517

429

409

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

110 Hz

91 Hz

100 Hz

90 Hz

An observer standing at 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 is ____.

At what speed should a source of sound move so that stationary observer finds the apparent frequency equal to half of the original frequency?

v

2v

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 / s ____.

4

8

2

Zero

The driver of a car traveling with speed 30 metres per second towards a hill sounds a horn of frequency 600 Hz. If the velocity of sound in air is 330 metres per second, the frequency of the reflected sound as heard by the driver is ____.

500 Hz

550 Hz

555.5 Hz

720 Hz

A source of sound is traveling with a velocity 40 km / hour towards observer and emits sound of frequency 2000 Hz. If velocity of sound is 1220 km / hour, then what is the apparent frequency heard by an observer ____.

2086 Hz

2068 Hz

1920 Hz

2210 Hz

A source of sound and listener are approaching each other with a speed of 40 m/s. The apparent frequency of note produced by the source is 400 cps. Then, its true frequency (in cps) is (velocity of sound in air = 360 m/s) ____.

320

400

360

420

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

286.5 Hz

481.2 Hz

589.3 Hz

434.2 Hz

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

the apparent frequency as heard by him is smaller than 600 Hz

the apparent frequency is larger than 600 Hz

the frequency as heard by him is 600 Hz

None of the above

A source of sound of frequency 500 Hz is moving towards an observer with velocity 30 m/s. The speed of sound is 330 m/s. the frequency heard by the observer is ____.

550 Hz

458.3 Hz

530 Hz

545.5 Hz

A source of sound of frequency 90 vibrations/ s is approaching a stationary observer with a speed equal to the speed of sound. What is the frequency heard by the observer ____.

80 vibrations/s

90 vibrations/s

100 vibrations/s

120 vibrations/s

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) ____.

436 to 586

426 to 574

426 to 584

436 to 674

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

INCREASES

DECREASES

CAN NOT BE PREDICTED

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) ____.

1950 Hz

2068 Hz

2132 Hz

2486 Hz

A source is moving towards an observer with a speed of 20 m/s and having frequency of 240 Hz. The observer is now moving towards the source with a speed of 20 m/s. Apparent frequency heard by observer, if velocity of sound is 340 m/s, is ____.

240 Hz

270 Hz

280 Hz

360 Hz

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**Description:**

This test includes questions from Wave and sound and also from Doppler's Effect

**Discussion**

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