State any two characteristics of a plane progressive wave.

Explanation

To answer the question regarding the characteristics of a plane progressive wave, we can break down the solution into clear steps:

### Step-by-Step Solution:

1. **Understanding Plane Progressive Waves**:
- A plane progressive wave is a type of wave that travels through a medium in a uniform manner. It can be visualized as a series of crests and troughs that move in a specific direction.

2. **Characteristic 1**:
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