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Chapter 16: Q. 66 (page 453)
An AM radio station broadcasts with a power of 25 kW at a
frequency of 920 kHz. Estimate the intensity of the radio wave at a point 10 km from the broadcast antenna.
The intensity of the radio wave is
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A mother hawk screeches as she dives at you. You recall from biology that female hawks screech at 800 Hz, but you hear the screech at 900 Hz. How fast is the hawk approaching?
Sound wave A delivers 2 J of energy in 2 s. Sound wave B delivers 10 J of energy in 5 s. Sound wave C delivers 2 mJ of energy in 1 ms. Rank in order, from largest to smallest, the sound powers PA, PB, and PC of these three sound waves. Explain
During takeoff, the sound intensity level of a jet engine is 140 dB at a distance of 30 m. What is the sound intensity level at a distance of 1.0 km?
A communications truck with a 44-cm-diameter dish receiver on the roof starts out 10 km from its base station. It drives directly away from the base station at 50 km/h for 1.0 h, keeping the receiver pointed at the base station. The base station antenna broadcasts continuously with 2.5 kW of power, radiated uniformly in all directions. How much electromagnetic energy does the truck’s dish receive during that 1.0 h?
A concert loudspeaker suspended high above the ground emits 35 W of sound power. A small microphone with a 1.0 cm2 area is 50 m from the speaker. a. What is the sound intensity at the position of the microphone? b. How much sound energy impinges on the microphone each second?
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