A magnet having a magnetic dipole moment ' M is placed in two magnetic fields ' \( B_1 \) ' and ' \( B_2 \) ' respectively. If it is displaced slightly from the equilibrium position, it oscillates $60$ times in $20$ second in field ' \( B_1 \) ' and $60$ times in $30$ second in field ' \( B_2 \) '. The ratio of field ' \( B_1 \) ' to that of ' \( B_2 \) ' is
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- $T \propto \frac{1}{\sqrt{B}}$
- Use oscillations/time to find period