In a direction magnetometer experiment in "tan" A position, a short bar magnet placed at 18 cm from the centre of the compass needle produces a deflection of `30^(@)`. If another magnet of same length but 16 times pole strength as that of first magnet is placed "tan"B position at 36 cm, the deflection will be

Options

A. `0^(@)`
B. `30^(@)`
C. `45^(@)`
D. `60^(@)`

Answer

B

Explanation

In "tan"A position B"tan"`theta_(1)=(mu_(0))/(4pi)(2(M_(1)xx2l))/(d_(1)^(3))`
In "tan"B position B"`tantheta_(2)=(mu_(0))/(4pi)((M_(2)xx2l))/(d_(2)^(3))`
`("tan"theta_(1))/("tan"theta_(2))=2(m_(1)/(m_(2)))((d_(2))/(d_(1)))^(3)`
`implies "tan"theta_(2)="tan"30^(@)`
`therefore theta_(2)=30^(@)`