(A ): In electromagnetic wave, electric and magnetic fields oscillate in the same plane and in the same phase. (R) Electric field is the primary energy carrier in the electromagnetic wave.

Options

A. Both 'A' and 'R' are true and 'R' is the correct explanation of 'A'.
B. Both 'A' and ’R' are true and 'R' is not the correct explanation of 'A
C. A' is true and 'R' is false
D. 'A' is false and R' is true

Answer

To analyze the assertion and reason provided in the question, we will evaluate each statement step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that in an electromagnetic wave, the electric and magnetic fields oscillate in the same plane and in the same phase.
- In reality, electromagnetic waves consist of oscillating electric (E) and magnetic (B) fields that are perpendicular to each other and also to the direction of wave propagation.

2. **Visualizing the Fields**:
- If we consider a three-dimensional coordinate system, we can represent the electric field oscillating in the x-y plane.
- The magnetic field oscillates in a plane that is perpendicular to the electric field, which means it will be in the z-direction if the electric field is in the x-y plane.

3. **Conclusion on the Assertion**:
- Since the electric and magnetic fields are not in the same plane (they are perpendicular), the assertion is **incorrect**.

4. **Understanding the Reason**:
- The reason states that the electric field is the primary energy carrier in the electromagnetic wave.
- In electromagnetic waves, both electric and magnetic fields carry energy, but the energy density associated with the electric field is indeed greater than that of the magnetic field.

5. **Conclusion on the Reason**:
- Since the electric field strength is generally much stronger than the magnetic field strength in electromagnetic waves, the reason is **correct**.

6. **Final Evaluation**:
- Based on our analysis, the assertion (A) is false, and the reason (R) is true. Therefore, we conclude that A is false and R is true.

### Summary:
- **Assertion (A)**: False (Electric and magnetic fields oscillate in perpendicular planes, not the same plane).
- **Reason (R)**: True (Electric field is the primary energy carrier in electromagnetic waves).