A dip circle is at right angles to the magnetic meridian. What will be the apparent dip ?

Options

A. (a) `0^(@)`
B. (b) `30^(@)`
C. (c) `60^(@)`
D. (d) `90^(@)`

Answer

To solve the problem of finding the apparent dip when a dip circle is at right angles to the magnetic meridian, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definitions**:
- **True Dip (y)**: The angle that the magnetic field makes with the horizontal plane.
- **Apparent Dip (x1)**: The angle that the magnetic field appears to make with the horizontal when measured at a certain angle to the magnetic meridian.
- **Angle with respect to Magnetic Meridian (x2)**: The angle between the dip circle and the magnetic meridian.

2. **Identify the Given Information**:
- The dip circle is at right angles to the magnetic meridian, which means \( x2 = 90^\circ \).

3. **Use the Relation Between True Dip, Apparent Dip, and Angle with Magnetic Meridian**:
- The relationship is given by the formula:
\[ \cot x1 = \cot y \cdot \cos x2 \]

4. **Substitute the Known Values**:
- Since \( x2 = 90^\circ \), we know that \( \cos 90^\circ = 0 \).
- Therefore, substituting into the equation gives:
\[ \cot x1 = \cot y \cdot 0 \]
- This simplifies to:
\[ \cot x1 = 0 \]

5. **Solve for Apparent Dip (x1)**:
- The cotangent of an angle is zero when the angle is \( 90^\circ \).
- Thus, we have:
\[ x1 = 90^\circ \]

6. **Conclusion**:
- The apparent dip when the dip circle is at right angles to the magnetic meridian is \( 90^\circ \).

### Final Answer:
The apparent dip is \( 90^\circ \).