Which of the following is the example of ideal black body?

Options

A. Kajal
B. Black board
C. A pin hole in a box
D. None of these

Explanation

To determine which of the following is an example of an ideal black body, we first need to understand the concept of a black body.

### Step 1: Define an Ideal Black Body
An ideal black body is an object that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. It does not reflect or transmit any light, making it appear perfectly black.

**Hint:** Remember that an ideal black body absorbs all light and does not reflect any.

### Step 2: Characteristics of a Black Body
An ideal black body not only absorbs all light but also emits energy perfectly when it radiates. This means it is also a perfect emitter of radiation.

**Hint:** Consider the properties of absorption and emission when identifying examples of black bodies.

### Step 3: Evaluate Common Examples
Common examples of materials that are often considered black bodies include:
- A blackened surface (like black paint)
- A blackboard
- A pinhole in a box

However, we must remember that not all of these examples qualify as ideal black bodies.

**Hint:** Think about whether the materials mentioned can absorb all light without reflecting any.

### Step 4: Analyze the Options
- **Kajal (eyeliner)**: While it is dark, it does not absorb all light perfectly.
- **Blackboard**: Similar to kajal, a blackboard does not absorb all light; it reflects some.
- **Pinhole in a box**: A pinhole in a box can be considered an ideal black body because the interior of the box absorbs all light that enters through the pinhole, making it appear black.

**Hint:** Focus on the concept of a pinhole in a box absorbing all light that enters it.

### Step 5: Conclusion
Based on the analysis, the best example of an ideal black body among the options provided is the **pinhole in a box**.

**Final Answer:** The example of an ideal black body is a **pinhole in a box**.

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