Assertion : Electromagnetic waves carry energy and momentum
Reason : Electromagnetic waves can be polarised.

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

Explanation

To solve the question regarding the assertion and reason statements related to electromagnetic waves, we will analyze each statement step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Electromagnetic waves carry energy and momentum."
- This is true. Electromagnetic waves, such as light, carry energy (which can be observed in phenomena like the photoelectric effect) and momentum (as evidenced by radiation pressure).

2. **Understanding the Reason**:
- The reason states that "Electromagnetic waves can be polarised."
- This is also true. Electromagnetic waves can exhibit polarization, which is a property that arises from their transverse nature. In polarization, the electric field vector can oscillate in a particular direction.

3. **Analyzing the Relationship**:
- While both the assertion and the reason are true, we need to determine if the reason explains the assertion.
- The ability of electromagnetic waves to be polarized does not directly explain why they carry energy and momentum. The energy and momentum of electromagnetic waves are a result of their oscillating electric and magnetic fields, not solely due to their ability to be polarized.

4. **Conclusion**:
- Since both statements are true, but the reason does not adequately explain the assertion, the correct conclusion is that the assertion is true, the reason is true, but the reason is not the correct explanation of the assertion.

### Final Answer:
- The correct answer is: **Both assertion and reason are true, but the reason is not the correct explanation of the assertion.**