Assertion: For two sources to be coherent phase difference between two waves at all points should be same.
Reason: Two different light sources are never coherent.

Options

A. If both Assertion and Reason are true and the Reason is correct explanation of the Assertion.
B. If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
C. If Assertion is true, but the Reason is false.
D. If Assertion is false but the Reason is true.

Explanation

To analyze the given assertion and reason, let's break it down step by step.

### Step 1: Understanding Coherence
Coherence refers to the property of two or more waves that allows for a stable and predictable interference pattern. For two sources to be considered coherent, the phase difference between the waves produced by these sources must remain constant over time.

**Hint:** Think about what it means for waves to interfere with each other and how their phase relationship affects the interference pattern.

### Step 2: Evaluating the Assertion
The assertion states that for two sources to be coherent, the phase difference between the two waves at all points should be the same. This is misleading. While the phase difference must be constant, it does not have to be the same at all points in space; it just needs to remain unchanged over time.

**Hint:** Consider the definition of coherence and how it relates to phase differences at different points in space.

### Step 3: Evaluating the Reason
The reason provided states that two different light sources are never coherent. This is generally true because different light sources (like a light bulb and a laser) emit light waves that can have varying frequencies and phases, making it impossible for them to maintain a constant phase relationship.

**Hint:** Reflect on the characteristics of different light sources and how they affect coherence.

### Step 4: Conclusion
Based on the analysis:
- The assertion is **false** because it incorrectly states that the phase difference must be the same at all points, rather than just constant over time.
- The reason is **true** because different light sources typically do not maintain coherence.

Thus, the assertion is false, and the reason is true.

**Final Answer:** Assertion is false, Reason is true.