alleryTwo planets orbit the same star with semi-major axes 1 AU and 4 AU. Ratio of their orbital periods T1 : T2 is:
A1 : 16
B1 : 4
C1 : 8
D1 : 2
Answer & Solution
Correct answer: C. 1 : 8
**By Kepler's third law:** T² ∝ r³.
T1²/T2² = (1/4)³ = 1/64. So T1/T2 = 1/8. Ratio is 1 : 8.
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