In two separate experiment the neutral point due to two small magnets are at a distance of r and 2r in broad side-on position. The ratio of their magnetic moments will be

Options

A. `4:1`
B. `1:2`
C. `2:1`
D. `1:8`

Answer

D

Explanation

At broad side-on position `B=M/d^(3)`
:. `M_(1)/d^(3)=M_(2)/d_(2)^(3)` or `M_(1)/r^(3)=M_(2)/(8r^(3))` or `M_(1)/M_(2)=r^(3)/(8r^(3))=1/8`