The angle of dip at a place is $60^{\circ}$. At this place,the total intensity of the Earth's magnetic field is $0.64 \text{ units}$. The horizontal intensity of the Earth's magnetic field at this place is . . . . . . $\text{units}$.

$A$ line passing through places having zero value of magnetic dip is called

$A$ magnetic compass needle oscillates $30$ times per minute at a place where the angle of dip is $45^{\circ}$,and $40$ times per minute where the angle of dip is $30^{\circ}$. If $B_1$ and $B_2$ are respectively the total magnetic field due to the earth at the two places,then the ratio $B_1/B_2$ is best given by:

If the angles of dip at two places are $30^{\circ}$ and $45^{\circ}$ respectively,then the ratio of horizontal components of earth's magnetic field at the two places will be

Let $V$ and $H$ be the vertical and horizontal components of the Earth's magnetic field at any point on Earth. Near the North Pole:

At a point $A$ on the earth's surface, the angle of dip is $\delta = +25^{\circ}$. At a point $B$ on the earth's surface, the angle of dip is $\delta = -25^{\circ}$. We can interpret that: