考场机经 test71
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Witnesses to a meteor in Australia in 1978 claimed to have heard strange noises as it streaked overhead. Yet, given that the meteor was 30 kilometers up, if these sounds had come directly from the meteor, people on the ground could not have heard them until almost a minute after the meteor had disappeared. Physicist Colin Keay hypothesized that the light given off by a meteor's trail must be accompanied by invisible electromagnetic radiation in the form of very low frequency (VLF) radio waves. Such waves, which travel at the speed of light, would reach the observer when the meteor itself came into view.

Subsequent experiments in a soundproof chamber showed that many things can act as transducers to convert VLF waves into audible vibrations. Aluminum foil, thin wires, pine needles, or dry hair all responded to a VLF field. VLF waves induce small charges in such objects, thereby causing them to vibrate in time with the waves' oscillation. This transducer effect would explain why some people heard the noises while others close by heard nothing. Those who heard sounds were simply nearer to transducers. It could also explain why attempts to record meteor sounds have failed: scientists carefully place their microphones away from possible sources of interference.

It can be inferred from the passage that if Keay’s proposed explanation of meteor sounds is correct, it is true that
A
meteors themselves produce no audible vibrations, even though the meteor does cause the sounds that observers hear.
B
when an observer hears the sounds, it is his or her own hair that is causing the audible vibrations.
C
if two observers in widely separated locations hear sounds caused by the same meteor, the audible vibrations that reach the observers are produced by different objects.
D
visible light and VLF radio waves are the only forms of electromagnetic radiation that are given off by a meteor's trail.
E
atmospheric conditions, such as clouds, that made a meteor invisible to observers on the ground would also prevent those observers from hearing any sounds caused by that meteor.
Select one answer choice.
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1.未作答
正确答案
1.C
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