The source of ultraviolet light is :

Options

A. A) electric bulb
B. B) red hot iron ball
C. C) sodium vapour lamp
D. D) carbon arc-lamp.

Answer

To determine the sources of ultraviolet (UV) light, we can analyze the options provided and identify which ones are known to emit UV rays.

### Step-by-Step Solution:

1. **Understanding Ultraviolet Light**:
- Ultraviolet light is a type of electromagnetic radiation with wavelengths shorter than visible light but longer than X-rays. It is commonly associated with sunlight.

2. **Identifying Common Sources of UV Light**:
- The most well-known source of UV light is the **Sun**. Sunlight contains UV rays, which are responsible for effects like sunburn.

3. **Considering Other Sources**:
- **Electric Bulbs**: Certain types of electric bulbs, especially fluorescent lamps, emit UV light as a byproduct of their operation.
- **Red Hot Iron**: When iron is heated to a high temperature, it can emit UV radiation due to its thermal radiation.
- **Sodium Vapor Lamps**: These lamps, commonly used in street lighting, also emit UV light as part of their spectrum.

4. **Conclusion**:
- Based on the analysis, the sources of ultraviolet light include:
- Sunlight
- Electric bulbs
- Red hot iron
- Sodium vapor lamps
- Therefore, the correct options for the sources of ultraviolet light are options A, B, and C.

### Final Answer:
The sources of ultraviolet light are:
- Sunlight
- Electric bulbs
- Red hot iron
- Sodium vapor lamps