The time of vibration of a dip needle vibration in the vertical plane in the magnetic needle is made to vibrate in the horizontal plane, the time of vibration is `3sqrt2 s`. Then angle of dip will be-

Options

A. `90^(@)`
B. `60^(@)`
C. `45^(@)`
D. `30^(@)`

Answer

B

Explanation

In magnetic meridian `3 = 2pi sqrt((I)/(MB_(e))) …(1)`
In horizontal plane, `3 sqrt(2) = 2pi sqrt((I)/(MH)) …(2)`
`therefore (3)/(3sqrt(2)) = sqrt((H)/(B_(e))) = sqrt((B_(e) costheta)/(B_(e))) rArr 0 = 60^(@)`