What is a lens ? Name the two types of lenses. Name any five things which use lenses.

Explanation

### Step-by-Step Solution

**Step 1: Define a Lens**
A lens is a transparent optical device made of glass or other transparent materials that refracts (bends) light rays passing through it. Lenses can focus light to a point or spread it out, depending on their shape.

**Step 2: Identify the Two Types of Lenses**
There are two main types of lenses:
1. **Convex Lens**: This lens is thicker in the middle than at the edges and converges light rays to a point.
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