The period of revolution of a certain planet in an orbit

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The period of revolution of a certain planet in an orbit of radius R is T. Its period of revolution in an orbit of radius 4R will be:

1. 8 T
2. 4 T
3. 2 √2 T
4. 2 T

Correct Option: A

Using Kepler’s Third Law,

	T²	=		R		³
	T₁²			4R

⇒ T₁ 8T