Classify the objects or materials given below as opaque, transparent or translucent and luminous or non-luminous:
smoke

Explanation

To classify smoke as opaque, transparent, or translucent, and as luminous or non-luminous, we can follow these steps:

### Step 1: Understand the Definitions
- **Opaque Objects**: These do not allow light to pass through. You cannot see through them.
- **Transparent Objects**: These allow light to pass through completely, and you can see clearly through them.
- **Translucent Objects**: These allow some light to pass through but scatter it, so objects behind them appear blurred or unclear.
- **Luminous Objects**: These emit their own light.
- **Non-Luminous Objects**: These do not emit light but can reflect it.
...