State the condition for constructive interference.

Explanation

To state the condition for constructive interference, we can break it down into the following steps:

### Step 1: Understand Interference
Interference occurs when two or more waves overlap and combine to form a new wave pattern. This can result in regions of increased amplitude (constructive interference) or decreased amplitude (destructive interference).

### Step 2: Define Path Difference
The path difference is the difference in the distance traveled by two waves arriving at the same point. For constructive interference to occur, this path difference must meet specific criteria.

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