Physics
For an echo, the reflected sound must reach the person at least …………… after the original sound is heard.
- 1 s
- 10 s
- 0.1 s
- 0.01 s
Sound
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Answer
0.1 s
Reason — For an echo to be heard, the reflected sound must reach the listener's ears at least 0.1 seconds (or 100 milliseconds) after the original sound is produced. If the reflected sound arrives sooner than this, it is perceived as part of the original sound rather than as a distinct echo.
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