For transmission of heat from one place to the other medium is required in

Options

A. conduction
B. convection
C. radiation
D. both (a) and (b)

Explanation

To solve the question "For transmission of heat from one place to the other, a medium is required in:", we need to analyze the three modes of heat transfer: conduction, convection, and radiation.

### Step-by-Step Solution:

1. **Understand the Modes of Heat Transfer**:
- **Conduction**: This is the process of heat transfer through direct contact between materials. When two objects at different temperatures are in contact, heat flows from the hotter object to the cooler one. This process requires a medium (solid, liquid, or gas) for the heat to be conducted.

2. **Analyze Convection**:
- **Convection**: This mode involves the transfer of heat by the movement of fluids (liquids and gases). When a fluid is heated, it becomes less dense and rises, while cooler fluid moves in to take its place. This process also requires a medium (liquid or gas) to facilitate the movement of the heated particles.

3. **Examine Radiation**:
- **Radiation**: Unlike conduction and convection, radiation does not require a medium for heat transfer. Heat can be transferred through electromagnetic waves (like infrared radiation) even in a vacuum. This means that heat can be transmitted from the sun to the Earth without any medium.

4. **Conclusion**:
- Since the question asks for the modes of heat transfer that require a medium, we can conclude that conduction and convection both require a medium for heat transfer. Radiation, on the other hand, does not require any medium.

### Final Answer:
The answer is **Conduction and Convection**.

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