The period of revolution of an earth satellite close to surface of earth is 90 min. The time period of another satellite in an orbit at a distance of three times the radius of earth from its surface will be
720 min
Distance of second satellite from the centre of earth has become four times.
Now T2∝r3 or T∝r32
∴ Time period of second satellite will become (4)32 or 8 times.
Hence T'= 8T = (8) (90) = 720 min