Differential between a ray and a wavefront.

Explanation

To differentiate between a ray and a wavefront, we can break down the definitions and characteristics of each concept step by step.

### Step-by-Step Solution:

1. **Definition of a Ray**:
- A ray is defined as an imaginary line that represents the direction of propagation of a wave. It indicates the path along which the energy of the wave travels.
- **Example**: If you imagine a flashlight, the beam of light emitted can be represented by rays that extend outward in straight lines from the source.

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