Give two uses of periscopes.

Explanation

### Step-by-Step Solution:

1. **Understanding the Periscope**: A periscope is an optical device that allows an observer to see objects that are not in their direct line of sight. It typically consists of two mirrors positioned at an angle to reflect light from an object to the observer's eyes.

2. **Identifying Uses**: We need to identify two practical applications of periscopes in real-world scenarios.

3. **First Use - Submarines**: One of the primary uses of periscopes is in submarines. Submarines operate underwater and cannot see the surface directly. A periscope allows the crew to view the surface of the water while remaining submerged, providing essential information about the surroundings.

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