Lux is the unit of

Options

A. (a)Intensity of illumination
B. (b)luminous efficiency
C. (c)luminuous flux
D. (d)luminous intensity

Answer

To solve the question "Lux is the unit of", we will go through the definitions and relationships of different units related to light and illumination.

### Step-by-Step Solution:

1. **Understanding Luminous Intensity**:
- Luminous intensity is defined as the amount of light emitted from a source in a particular direction. The unit for luminous intensity is the **candela (cd)**.

**Hint**: Remember that luminous intensity refers to the light emitted in a specific direction.

2. **Understanding Luminous Flux**:
- Luminous flux refers to the total amount of light emitted by a source, and its unit is the **lumen (lm)**.

**Hint**: Luminous flux is about the total light output, not just the intensity in one direction.

3. **Understanding Luminous Efficiency**:
- Luminous efficiency is a measure of how well a light source produces visible light and is dimensionless, meaning it does not have a unit.

**Hint**: Since it is dimensionless, it does not contribute to our search for a unit.

4. **Understanding Intensity of Illumination**:
- The intensity of illumination (or illuminance) is defined as the amount of luminous flux per unit area. The unit of illuminance is the **lux (lx)**.

**Hint**: Think of illuminance as how much light falls on a surface area.

5. **Defining Lux**:
- Lux is defined as one lumen per square meter. Therefore, when we say "lux is the unit of", we can conclude that it measures the intensity of illumination.

**Hint**: Remember that lux quantifies how much light is received on a surface area.

6. **Final Answer**:
- Based on the definitions and relationships, we conclude that **lux is the unit of illumination**.

### Conclusion:
The answer to the question "Lux is the unit of" is that it is the unit of **illumination**.