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Who developed the theory of relativity? सापेता का सांत कसनेवकसत कया था? Options: 1) Issac Newton आइज़ैक यूटन 2) Charles Darwin चासडावन 3) Marie Curie मैर यूर 4) Albert Einstein अबटआइंटन

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What is the minimum distance (in metres) required to hear an echo? ितिन सुननेके िलए ूनतम दू री (मीटर म) िकतनी होनी चािहए? Options: 1) 10 2) 13 3) 17 4) 21

Correct Answer: 17The velocity of sound in dry air is approximately 343 m/s at a temperature of 25 °C. Therefore, the reflecting object must be more than 17.2m from the sound source for echo to be perceived by a person located at the source....Read more