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
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 = 340 m/s) ____.
333 Hz
374 Hz
385 Hz
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) ____.
733.3 Hz
644.8 Hz
481.2 Hz
286.5 Hz
A source emits a sound of frequency of 400 Hz, but the listener hears it to be 390 Hz. Then ____.
the listener is moving towards the source
the source is moving towards the listener
the listener is moving away from the source
the listener has a defective ear
A source and an observer are moving towards each other with a speed equal to where be the speed of sound. The source is emitting sound of frequency n. The frequency heard by the observer is ____.
Zero
/
540 m/s
270 m/s
85 m/s
52.5 m/s
A police car horn emits a sound at a frequency 240 Hz when the car is at rest. If the speed of the sound is 330 m/s, the frequency heard by an observer who is approaching the car at a speed of 11 m/s, is ____.
248 Hz
244 Hz
240 Hz
230 Hz
A bus is moving with a velocity of 5 m/s towards a huge wall. The driver sounds a horn of frequency 165 Hz. If the speed of sound in air is 355 m/s, the number of beats heard per second by a passenger on the bus is ____.
6
5
3
4