Assertion : For revolving electron, direction of angular momentum and magnetic moment are opposite.
Reason : Charge of electron is negative.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Answer

To solve the given question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding Angular Momentum**:
- The angular momentum \( \vec{L} \) of a particle moving in a circular path is given by the formula:
\[ \vec{L} = \vec{r} \times \vec{p} \]
where \( \vec{r} \) is the position vector from the axis of rotation to the particle, and \( \vec{p} \) is the linear momentum of the particle.

2. **Direction of Angular Momentum**:
- For an electron moving in an anticlockwise direction, the direction of the angular momentum can be determined using the right-hand rule. If you curl the fingers of your right hand in the direction of the electron's motion (anticlockwise), your thumb will point upwards, indicating that the angular momentum vector \( \vec{L} \) points upwards.

3. **Understanding Magnetic Moment**:
- The magnetic moment \( \vec{\mu} \) due to a current loop is given by:
\[ \vec{\mu} = I \cdot \vec{A} \]
where \( I \) is the current and \( \vec{A} \) is the area vector of the loop. The direction of the area vector is given by the right-hand rule, which is also in the direction of the thumb when fingers curl in the direction of current flow.

4. **Direction of Current**:
- Since the electron has a negative charge, the conventional current \( I \) (which is the flow of positive charge) will flow in the opposite direction to the motion of the electron. Therefore, if the electron moves anticlockwise, the current will be considered to flow clockwise.

5. **Direction of Magnetic Moment**:
- Following the right-hand rule for the current flowing clockwise, the area vector \( \vec{A} \) will point downwards. Thus, the magnetic moment \( \vec{\mu} \) will also point downwards.

6. **Comparison of Directions**:
- We have established that:
- The angular momentum \( \vec{L} \) points upwards.
- The magnetic moment \( \vec{\mu} \) points downwards.
- Therefore, the direction of angular momentum and magnetic moment are indeed opposite.

7. **Conclusion**:
- The assertion is correct: for a revolving electron, the direction of angular momentum and magnetic moment are opposite.
- The reason is also correct: the charge of the electron is negative, which leads to the opposite directions of current and magnetic moment compared to the angular momentum.

### Final Answer:
Both the assertion and the reason are correct.