The correct option is
C 17:8The time period of a magnetic dipole is given by
T=2π√IMBH
Here, I is the moment of Inertia, M is the magnetic moment and BH is the horizontal component of Earth's magnetic field.
When two magnets are linked together, let I′ be the new moment of inertia.
Let M1, M2 be the magnetic moments of individual magnets.
If similar poles are together, new magnetic moment of the combined system is M1+M2
If dissimilar poles are together, new magnetic moment of the combined system is M1−M2
Therefore, T1T2=√M1+M2M1−M2
⇒(106)2=M1+M2M1−M2⇒M1M2=25+925−9=178
Thus,M1:M2=17:8