The height in terms of radius of the earth \( (R) \), at which the acceleration due to gravity becomes \( \frac{g}{9} \), where \( g \) is acceleration due to gravity on earth's surface, is
\( \sqrt{3}\,R \)
\( 2\sqrt{2}\,R \)
\( 2R \)
\( \frac{4}{9}R \)