Finger prints on a piece of paper may be detected by sprinkling flourescent powder on the paper and then looking it into

Options

A. dark-light
B. sun-light
C. infra-red-light
D. ultraviolet light

Answer

To solve the question regarding how fingerprints on a piece of paper can be detected using fluorescent powder, we can break down the process step by step:

### Step-by-Step Solution:

1. **Understanding the Problem**:
- The question asks how fingerprints on paper can be detected after sprinkling fluorescent powder.

2. **Fluorescent Powder**:
- Fluorescent powder is used because it can absorb light and then re-emit it at a different wavelength. This property is crucial for making invisible fingerprints visible.

3. **Application of Ultraviolet Light**:
- When the fluorescent powder is applied to the fingerprints, it adheres to the oils and residues left by the fingers.
- The next step involves illuminating the paper with a specific type of light.

4. **Detection with Ultraviolet Light**:
- Ultraviolet (UV) light is used because it excites the fluorescent powder, causing it to glow.
- This glow makes the previously invisible fingerprints visible against the background of the paper.

5. **Conclusion**:
- Therefore, the correct answer to the question is that fingerprints can be detected by looking at the paper under ultraviolet light.

### Final Answer:
Fingerprints on a piece of paper may be detected by sprinkling fluorescent powder on the paper and then looking at it under ultraviolet light.

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