A magnetic needle free to rotate in a vertical plane parallel to magnetic meridian has its north tip down at `60^@` with the horizontal. The horizontal component of earth's magnetic field at that place is `0*4G`. Determine the magnitude of earth's magnetic field at the place.

Explanation

To solve the problem, we need to determine the magnitude of the Earth's magnetic field at a location where the horizontal component of the magnetic field (Bh) is given, and the angle of dip (δ) is known.

### Step-by-Step Solution:

1. **Identify the Given Values:**
- Horizontal component of Earth's magnetic field, \( B_H = 0.4 \, \text{G} \)
- Angle of dip, \( \delta = 60^\circ \)

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