Mention one property which is caused due to the presence of F-centre in a solid

Explanation

To answer the question regarding one property caused by the presence of F-centres in a solid, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding F-centres**:
- F-centres are defects in ionic solids where an anion vacancy is created, and an electron occupies this vacancy. This results in the formation of a color center.

2. **Effect on Color**:
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