Explain why echoes are also used in SONAR.

Explanation

**Step-by-Step Solution:**

1. **Understanding SONAR**: SONAR stands for Sound Navigation and Ranging. It is a technique that uses sound waves to detect objects underwater.

2. **The Concept of Echo**: An echo is the reflection of sound waves. When sound waves hit an object, they bounce back, creating an echo that can be detected.

3. **Application in Submarines**: In underwater environments, visibility is often very low. Submarines use SONAR to navigate and detect obstacles like rocks or the seabed.

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