MCQ
Vibration magnetometer before use, should be set
- ✓In magnetic meridian
- BIn geographical meridian
- CPerpendicular to magnetic meridian
- DIn any position
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Reason : In $\alpha - $decays the mass number decreases by $4$ and atomic number decreases by $2$. In $2\beta - $ decays the mass number remains unchanged, but atomic number increases by $1$ only.