The acceleration due to gravity at a height 1 km above the earth is the same as at a depth d below the surface of earth. Then, [NEET 2017]

Acceleration due to gravity at height h above earth's surface,gh=g1-2hR                       (∵h≪R)Acceleration due to g:t:avity at depth d below earth's surface,gd=g1-dRGiven, h = 1km and gd = ghor       g1-dR=g1-2hR⇒  d=2h or d=2 km