Exam 17: Waves in Two and Three Dimensions

You are driving along a highway at 35.0 m/s when you hear the siren of a police car approaching you from behind and you perceive the frequency as 1310 Hz.You are relieved that he is in pursuit of a different speeder when he continues past you,but now you perceive the frequency as 1240 Hz.What is the frequency of the siren in the police car? The speed of sound in air is 343 m/s.

A carousel that is 5.00 m in radius has a pair of 600-Hz sirens mounted on posts at opposite ends of a diameter.The carousel rotates with an angular velocity of 0.800 rad/s. A stationary listener is located at a distance from the carousel.The speed of sound is 350 m/s.The maximum beat frequency of the sirens at the position of the listener is closest to

An enclosed chamber with sound absorbing walls has a 2.0 m × 1.0 m opening for an outside window.A loudspeaker is located outdoors,84 m away and facing the window.The intensity level of the sound entering the window space from the loudspeaker is 56 dB.Assume the acoustic output of the loudspeaker is uniform in all directions and that acoustic energy incident upon the ground is completely absorbed and therefore is not reflected into the window.The threshold of hearing is 1.0 × 10^-12 W/m².The acoustic power output of the loudspeaker is closest to

A carousel that is 5.00 m in radius has a pair of 600-Hz sirens mounted on posts at opposite ends of a diameter.The carousel rotates with an angular velocity of 0.800 rad/s. A stationary listener is located at a distance from the carousel.The speed of sound is 350 m/s.The longest wavelength reaching the listener from the sirens is closest to

A jet aircraft,in level flight at constant speed,is observed directly overhead.A sonic boom is heard later,at which time the line of sight to the aircraft forms a 56° angle with respect to the horizontal.The speed of sound is 325 m/s.What is the Mach number (the ratio of the speed of the jet to the speed of sound)for the aircraft?

A boy on a bicycle approaches a brick wall as he sounds his horn at a frequency 400.00 Hz. The sound he hears reflected back from the wall is at a frequency 408.00 Hz. At what is the speed is the boy riding his bicycle toward the wall? Assume the speed of sound in air is 340 m/s.

You are driving along a highway at 35.0 m/s when you hear the siren of a police car approaching you from behind and you perceive the frequency as 1370 Hz.You are relieved that he is in pursuit of a different speeder when he continues past you,but now you perceive the frequency as 1330 Hz.What is the speed of the police car? The speed of sound in air is 343 m/s.

A stationary siren emits sound of frequency 1000 Hz and wavelength 0.343 m.An observer who is moving toward the siren will measure a frequency f and wavelength λ for this sound such that

A person is hearing two sound waves simultaneously.One has a period of 1.50 ms and the other one a period of 1.54 ms.What is the period of the beat due to these two waves?

The intensity level of a "Super-Silent" power lawn mower at a distance of 1.0 m is 100 dB.You wake up one morning to find that four of your neighbors are all mowing their lawns using identical "Super-Silent" mowers.When they are each 20 m from your open bedroom window,what is the intensity level of the sound in your bedroom? You can neglect any absorption,reflection,or interference of the sound.The lowest detectable intensity is 1.0 × 10^-12 W/m².

The tension in each of two strings is adjusted so that both vibrate at exactly 666 Hz.The tension in one of the strings is then increased slightly.As a result,six beats per second are heard when both strings vibrate.What is the new frequency of the string that was tightened?

Observer A is 3.0 m from a tiny light bulb and observer B is 12.0 m from the same bulb.Assume that the light spreads out uniformly and undergoes no significant reflections or absorption.If observer B sees a light of intensity I,the light intensity that A sees is

Two motors in a factory are running at slightly different rates.One runs at 825 rpm and the other at 786 rpm.You hear the sound intensity increase and then decrease periodically due to wave interference.How much time elapses between successive maxima of the sound intensity?

A policeman in a stationary car measures the speed of approaching cars by means of an ultrasonic device that emits a sound with a frequency of 41.2 kHz.A car is approaching him at a speed of 33.0 m/s.The wave is reflected by the car and interferes with the emitted sound producing beats.What is the frequency of the beats? The speed of sound in air is 330 m/s.

A woman is riding a bicycle at 18.0 m/s along a straight road that runs parallel to and right next to some railroad tracks.She hears the whistle of a train that is behind.The frequency emitted by the train is 840 Hz,but the frequency the woman hears is 778 Hz.Take the speed of sound to be 340 m/s. (a)What is the speed of the train,and is the train traveling away from or toward the bicycle? (b)What frequency is heard by a stationary observer located between the train and the bicycle?

Calculate the light intensity 1.51 m from a light bulb that emits 100 W of visible light,assuming that the light radiates uniformly in all directions.

A plane flies toward a stationary siren at 1/4 the speed of sound.Then the plane stands still on the ground and the siren is driven toward it at 1/4 the speed of sound.In both cases,a person sitting in the plane will hear the same frequency of sound from the siren.

A sound source emits 20.0 W of acoustical power spread equally in all directions.The threshold of hearing is 1.0 × 10^-12 W/m².What is the sound intensity level 30.0 m from the source?

An airplane flying faster than the speed of sound of 340 m/s produces a shock wave that makes an angle of 50° with the direction the plane is flying.What is the speed of the plane?

Which one of the following statements is true?