The angle of dip `0^(@) and 90^(@)` respectively are at:

Options

A. North pole, South pole
B. Equator, poles
C. Poles, equator
D. Both (a) and (c)

Explanation

To solve the question regarding the angle of dip at 0° and 90°, we need to understand the concept of magnetic dip and how it varies with geographic location.

### Step-by-Step Solution:

1. **Understanding the Angle of Dip**:
- The angle of dip (or magnetic inclination) is the angle made with the horizontal by the Earth's magnetic field lines. It varies depending on the location on Earth.

2. **Angle of Dip at the Equator**:
- At the equator, the magnetic field lines are horizontal. Therefore, the angle of dip is 0°. This means that the vertical component of the magnetic field (BV) is zero, and the horizontal component (BH) is at its maximum.

3. **Angle of Dip at the Magnetic Poles**:
- At the magnetic poles, the magnetic field lines are vertical. Therefore, the angle of dip is 90°. Here, the horizontal component (BH) is zero, and the vertical component (BV) is at its maximum.

4. **Mathematical Representation**:
- The relationship between the vertical component (BV), horizontal component (BH), and the angle of dip (θ) can be expressed as:
\[ \tan(\theta) = \frac{BV}{BH} \]
- For θ = 0° (equator):
\[ \tan(0°) = \frac{0}{BH} \implies BV = 0 \]
- For θ = 90° (magnetic poles):
\[ \tan(90°) = \frac{BV}{0} \implies BH = 0 \]

5. **Conclusion**:
- Therefore, the angle of dip is 0° at the equator and 90° at the magnetic poles.

### Final Answer:
- The angle of dip is 0° at the equator and 90° at the magnetic poles.