televised live. The ng 20. G A politician holds a press conference that is sound
ID: 2036361 • Letter: T
Question
televised live. The ng 20. G A politician holds a press conference that is sound picked up by the microphone of a TV news network is broadcast via electromagnetic waves and heard by a television viewer. This viewer is seated 2.3 m from his television set. A reporter at the press conference is located 4.1 m from the politician, and the sound of the words travels directly fron the celebrity's mouth, through the air, and into the reporters ears. The reporter hears the words exactly at the same instant that the tele- vision viewer hears them. Using a value of 343 m/s for the speed of sound, determine the maximum distance between the television set and the politi- cian. Ignore the small distance between the politician and the microphone. In addition, assume that the only delay between what the microphone picks up and the sound being emitted by the television set is that due to the travel time of the electromagnetic waves used by the network stri 32.Explanation / Answer
Speed of sound v = 343 m/s
Time taken by sound in reaching the viewer from tv set located at a distance 2.3 m is given by:
Tv = 2.3/343 = 6.70554 x 10-3 s
Time taken by sound in reaching the reporter from the politician sitting 4.1 m is given by:
Tr = 4.1/343 s= 11.95335 x 10-3 s
Hence, time taken by em waves in travelling from politician to tv set is the difference between two times, because sound reaches both persons at same time.
T = (11.95335 - 6.70554 ) x 10-3 s = 5.24781 x 10-3 s
This time is taken by em waves which travel with speed of light : 3 x 108 m/s
Hence, max distance = 3 x 108 x 5.24781 x 10-3 = 1.574343 x 106 m
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