At a certain place on earth, the north tip of the magnetic needle of a dip circle placed in the plane of magnetic meridian points 60° below the horizontal. The horizontal component of the earth's magnetic field is measured to be 0.16 G. The magnitude of the earth's magnetic field at the location is:

0.32 G

The correct answer is Option (3) → 0.32 G

Magnitude of Earth's magnetic field $(\vec B)$ is -

$B=\frac{B_H}{\cos δ}$  [$δ$ = Angle of Dip]

Given,

$B_H=0.16G$

$δ=60°$

$B=\frac{B_H}{\cos δ}=\frac{0.16}{5}=0.32G$