What are polaroids ? Mention some of their practical uses ?

Explanation

### Step-by-Step Solution:

**Step 1: Definition of Polaroids**
- Polaroids are materials that have the ability to polarize light. This means they can filter light waves so that only certain orientations of light are allowed to pass through.

**Step 2: Understanding Polarization**
- When light is emitted from a source, it consists of waves vibrating in all possible directions. When this light passes through a polaroid, only the components of the light waves that are aligned with the polaroid's axis will pass through. This process of filtering is known as polarization.

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