Which one of the following is used for Sun glasses?
धूप के चश्मे के लिए किस काँच का प्रयोग किया जाता है?

Options

A. Pyrex glass/पाइरेक्स काँच
B. Flint glass/फ्लिंट काँच
C. Crooks glass/क्रुक्स काँच
D. Crystal glass/क्रिस्टल काँच

Explanation

To determine which type of glass is used for sunglasses, we need to analyze the properties of the given options: Pyrex glass, Flint glass, Crook's glass, and Crystal glass.

### Step-by-Step Solution:

1. **Understanding the Requirements for Sunglasses:**
- Sunglasses must have high absorption qualities to effectively block harmful UV rays.
- They should ideally contain cerium, which enhances their ability to absorb high-energy visible light.

2. **Evaluating the Options:**
- **Pyrex Glass:** This type of glass is known for its thermal resistance and is commonly used in laboratory glassware. It does not have the necessary properties for UV protection.
- **Flint Glass:** While this glass has some optical properties, it does not provide adequate UV protection or contain cerium.
- **Crystal Glass:** This glass is often used for decorative items and does not possess the required absorption qualities for sunglasses.
- **Crook's Glass:** This type of glass is specifically designed to absorb UV rays and contains cerium, making it suitable for sunglasses.

3. **Conclusion:**
- Based on the properties evaluated, the correct option for sunglasses is **Crook's glass**.

### Final Answer:
The type of glass used for sunglasses is **Crook's glass**.