# Kirchhoff's Law of Thermal Radiation

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**Formula:**`E = σ * A * T`

^{4}

## Introduction to Kirchhoff's Law of Thermal Radiation

Kirchhoff's law of thermal radiation states that for a body in thermal equilibrium, the emissive power is directly proportional to the absorptivity and the area of the body. This law is widely used in engineering and physics to analyze and design thermal systems, such as in the field of solar energy, electronics, and materials science. The formula for the emissive power is given by ** E = σ * A * T^{4}**, where

**is the emissive power,**

*E***is the Stefan-Boltzmann constant,**

*σ***is the area of the body, and**

*A***is the absolute temperature.**

*T*## Parameter usage:

`EmissivePower`

= emissive power of the body`Absorptivity`

= absorptivity of the body`Area`

= area of the body

## Output:

`E`

= emissive power of the body

## Data validation

The emissive power should be a positive number, the absorptivity should be between 0 and 1, and the area should be a positive number.

## Summary

This calculation allows for the determination of the emissive power of a body based on its absorptivity and area, providing valuable insights in thermal analysis and design.

Tags: Thermodynamics, Radiation, Emissive Power, Absorptivity