A body, which emits radiations of all possible wavelengths, is known as

Options

A. Good conductor
B. Partial radiator
C. Planks's law
D. Perfectly Black Body

Explanation

To solve the question, we need to identify the term that describes a body which emits radiations of all possible wavelengths.

### Step-by-Step Solution:

1. **Understanding the Concept of Black Body**:
A black body is defined as an idealized physical object that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. It does not reflect any light, which is why it appears black.

2. **Emission of Radiation**:
According to Kirchhoff's law of thermal radiation, a good absorber of radiation is also a good emitter. This means that a black body, which absorbs all wavelengths of radiation, will also emit radiation at all wavelengths.

3. **Characteristics of a Black Body**:
- It has 100% absorption of all incident radiation.
- It emits radiation across all possible wavelengths when in thermal equilibrium.
- It is a perfect radiator of heat.

4. **Conclusion**:
Therefore, the body that emits radiations of all possible wavelengths is known as a "black body."

### Final Answer:
A body, which emits radiations of all possible wavelengths, is known as a **black body**.

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