Two bar magnets are placed in vibration magnetometer and allowed to vibrate. They make `20` oscillations per minute when their similar pole are on the same side, while they make `15` osicillations per minute when their opposite poles lie on the same side. The ratio of their magnetic moments is

Options

A. `7:25`
B. `25:7`
C. `25:16`
D. `16:25`

Answer

C

Explanation

`n = (1)/(2pi)sqrt((mB_(H))/(I))`
`20 = 2pisqrt(((M_(1) + M_(2))B_(H))/(2I))`
`= 15 = 2pi 20 = 2pisqrt(((M_(1) - M_(2))B_(H))/(2I))`
`(4)/(3) = sqrt((M_(1) + M_(2))/(M_(1) - M_(2))`
Soving `(M_(1))/(M_(2)) = (25)/(7)`