MCQ
The line on the earth's surface joining the points where the field is horizontal is
- AMagnetic meridian
- BMagnetic axis
- CMagnetic line
- ✓Magnetic equator
The earth's magnetic field starts from the magnetic north pole and ends at the south one.
At the poles the field is perpendicular to the ground upto a certain height and then it curves and turns. Thus, at the pole, the field is completely vertical and has no horizontal component. This happens only at the poles.
At the magnetic equator, the field is completely horizontal and has no vertical component.
The line joining the geographic poles of the earth is known as geographic axis. The magnetic axis can be defined in a similar way. The two axes do not coincide and are slightly inclined to each other and they intersect at the centre. This is because the geographic poles and the magnetic poles do not coincide. The Magnetic field is independent of the geographic poles.
A latitude of the earth at a point on the earth surface is the angle made by the line joining that point and the earth's centre with the equatorial plane. At a latitude of $45^{0}$, the point on the earth surface is between the pole and the equator. Here the field has equal horizontal and vertical components.
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Reason : Because critical angle ${\theta _c} = {\sin ^{ - 1}}\,\left( {\frac{1}{\mu }} \right)$ and $\mu \, \propto \,\frac{1}{\lambda }$.