Two magnets are held together in a vibration magnetometer and are allowed to oscillate in the earth's magnetic field with like poles togather, 12 oscillations per minute are made but for unlike poles togather only 4 oscillations per minute are axecuted. The ratio of their magnetic miments is

Options

A. `3:1`
B. `1:3`
C. `3:5`
D. `5:4`

Answer

D

Explanation

In the sum and difference method of vibrration magnetometer
`M_(1)/M_(2)=(T_(2)^(2)+T_(1)^(2))/(T_(2)^(2)-T_(2)^(2))`
Here, `T_(1)=1/n_(1)=60/12=5 sec, T_(2)=1/n_(2)=60/4=15 sec`
`:. M_(1)/M_(2)=(15^(2)+5^(2))/(15^(2)-5^(2))=(225+25)/(225-25)=5/4`