Assertion (A) : The phase difference between any two points on a wave front is zero
Reason (R ) : Light from the source reaches every point of the wave front at the same time

Options

A. Statement-1 is true, statement-2 is true: Statement-2 is a correct explanation for statement-1
B. Statement-2 is true, statement-2 is true: statement-2 is not a correct explanation for statement-1
C. Statement-1 is true, Statement-2 is false.
D. Statement-1 is false, Statement-2 is true.

Answer

To solve the question, we need to analyze both the assertion (A) and the reason (R) provided.

### Step 1: Understanding the Assertion
The assertion states that "The phase difference between any two points on a wave front is zero."

- A wave front is defined as the locus of points that are in the same phase of oscillation. For a point source of light, the wave front is spherical, and all points on this wave front oscillate in unison. Therefore, the phase difference between any two points on the wave front is indeed zero.

### Step 2: Understanding the Reason
The reason states that "Light from the source reaches every point of the wave front at the same time."

- This is also true. Since all points on the wave front are equidistant from the source (for a spherical wave front), light travels the same distance to each point on the wave front at the same speed. Thus, they reach the wave front simultaneously.

### Step 3: Analyzing the Relationship Between Assertion and Reason
Now, we need to determine if the reason correctly explains the assertion.

- While both the assertion and the reason are true, the reason does not serve as an explanation for the assertion. The assertion is about the phase difference being zero, while the reason discusses the timing of light reaching the wave front. The phase difference being zero is a consequence of the nature of the wave front, not merely a result of the timing of light reaching those points.

### Conclusion
- Assertion (A) is true.
- Reason (R) is true.
- However, the reason (R) does not correctly explain the assertion (A).

### Final Answer
- Assertion (A) is true.
- Reason (R) is true, but it does not explain Assertion (A).

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