At certain places on earth, the angle of dip is 30°. If horizontal component of earth's magnetic field is H, then the total intensity of earth's magnetic field will be:

$\frac{2H}{\sqrt{3}}$

The correct answer is Option (4) → $\frac{2H}{\sqrt{3}}$

The total intensity of the earth Magnetic field, B is related to its horizontal component H and the angle of dip θ by following relationship -

$B=\frac{H}{\cos θ}$

$θ=30°⇒\cos 30°=\frac{\sqrt{3}}{2}$

$B=\frac{H}{\frac{\sqrt{3}}{2}}=\frac{2H}{\sqrt{3}}$