Properly cut diamond sparkles because

Options

A. atoms emit light
B. material has high refractive index
C. It reflects all light falling on it
D. Light which enters it suffer multiple total internal reflections

Explanation

To answer the question "Properly cut diamond sparkles because," we need to analyze the properties of diamonds and how they interact with light.

### Step-by-Step Solution:

1. **Understanding Diamond Composition**:
- Diamonds are made of carbon atoms arranged in a crystal lattice structure. They do not emit light on their own.

2. **Refractive Index**:
- Diamonds have a very high refractive index (approximately 2.42). This means that light travels more slowly in diamonds than in air.

3. **Total Internal Reflection (TIR)**:
- Due to the high refractive index, diamonds have a small critical angle. The critical angle is the angle of incidence above which total internal reflection occurs. For diamonds, this critical angle is about 24 degrees.
- When light enters the diamond at angles greater than this critical angle, it reflects back into the diamond rather than refracting out.

4. **Multiple Reflections**:
- A properly cut diamond has many facets (flat surfaces). When light enters the diamond, it can undergo multiple total internal reflections within these facets.
- Each time light reflects off a facet, it can change direction, allowing it to exit the diamond at various angles.

5. **Sparkling Effect**:
- The combination of the high refractive index and the multiple internal reflections causes the diamond to scatter light in many directions. This scattering of light creates the sparkling effect that is characteristic of well-cut diamonds.

6. **Conclusion**:
- Therefore, a properly cut diamond sparkles because it has a high refractive index, which leads to a small critical angle and results in multiple total internal reflections of light within the diamond.

### Final Answer:
A properly cut diamond sparkles because it has a high refractive index, which causes light to undergo multiple total internal reflections.

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