A hot and a cold body are kept in vacuum separated from each other. Which of the following cause decrease in temperature of the hot body

Options

A. Radiation
B. convection
C. Conduction
D. Temperature

Explanation

To solve the problem, we need to understand how heat transfer occurs between two bodies, especially in a vacuum. Here’s a step-by-step breakdown of the reasoning:

### Step 1: Understand the scenario
We have two bodies: one hot and one cold, placed in a vacuum. This means there is no medium (like air or water) between them.

**Hint:** Consider how heat transfer occurs in different mediums.

### Step 2: Identify the modes of heat transfer
There are three primary modes of heat transfer:
1. **Conduction** - transfer of heat through direct contact between materials.
2. **Convection** - transfer of heat through the movement of fluids (liquids or gases).
3. **Radiation** - transfer of heat in the form of electromagnetic waves.

**Hint:** Recall which modes of heat transfer require a medium and which do not.

### Step 3: Analyze the effect of vacuum
In a vacuum, there is no medium for conduction or convection to occur. Therefore, these two modes of heat transfer cannot take place between the hot and cold bodies.

**Hint:** Think about what happens to heat transfer when there is no material present.

### Step 4: Determine the applicable mode of heat transfer
The only mode of heat transfer that can occur in a vacuum is radiation. The hot body can lose heat by emitting infrared radiation, which will lead to a decrease in its temperature.

**Hint:** Remember that all bodies emit radiation based on their temperature.

### Step 5: Conclusion
Since the hot body can only lose heat through radiation in a vacuum, this is the process that causes the decrease in temperature of the hot body.

**Final Answer:** The decrease in temperature of the hot body is caused by **radiation**.

### Summary of Steps:
1. Identify the scenario (hot and cold bodies in a vacuum).
2. List the modes of heat transfer (conduction, convection, radiation).
3. Analyze the effect of vacuum on these modes.
4. Conclude that only radiation can occur, leading to a temperature decrease.