Distinguish between Sky wave and Space wave modes of propagation in a communication system.

Explanation

### Step-by-Step Solution

1. **Definition of Sky Waves and Space Waves**:
- **Sky Waves**: These are radio waves that are transmitted by reflecting off the ionosphere, which is a layer of the Earth's atmosphere that is ionized by solar and cosmic radiation.
- **Space Waves**: These are radio waves that travel directly from the transmitter to the receiver in a straight line, typically used in line-of-sight communication.

2. **Mode of Propagation**:
- **Sky Waves**: Propagation occurs through ionospheric reflection, where the waves undergo total internal reflection at the ionosphere.
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