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Q31 (IAS/2005) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Astronomy and astrophysics Answer Verified

Assertion (A): The same face of the Moon is always presented to the Earth.
Reason (R): The Moon rotates about its own axis in 27.3 days which is about the same time that it takes to orbit the Earth.

Result
Your answer: —  Â·  Correct: A

Explanation

Assertion (A) is true: The Moon is tidally locked to Earth, meaning it rotates on its axis at the exact same rate that it revolves around our planet. As a result, the same hemisphere (the "near side") is always facing Earth.

Reason (R) is also true and correctly explains (A): The Moon's sidereal period of rotation on its axis is approximately 27.3 days, which is identical to its orbital period around Earth. This precise match is known as synchronous rotation. Because it turns exactly once on its axis each time it orbits Earth, the same face of the Moon is always presented to us.

Therefore, both (A) and (R) are individually true, and (R) is the correct explanation of (A).

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