# Emissivity Calculator

Introduction

Calculating emissivity is crucial in various fields such as engineering, physics, and thermodynamics. Emissivity refers to the efficiency of a surface to emit thermal radiation compared to an ideal emitter, typically a blackbody. This article presents a simple and efficient calculator to determine emissivity.

## How to Use

To utilize the emissivity calculator, follow these steps:

- Enter the temperature of the surface.
- Input the temperature of the surrounding environment.
- Fill in the wavelength of interest (in micrometers).
- Click on the “Calculate” button to obtain the emissivity value.

## Formula

The formula used to calculate emissivity is given by:

\varepsilon = \frac{{\lambda_1}}{{\lambda_2}} \times \left( \frac{{e^{\frac{{hc}}{{k \cdot \lambda \cdot T}}}} – 1 \right)^{-1}

Where:

*ε*is the emissivity.*λ*1 is the upper limit of wavelength (in micrometers).*λ*2 is the lower limit of wavelength (in micrometers).*h*is Planck’s constant (6.62607015×10−346.62607015×10−34 m² kg / s).*c*is the speed of light (2.998×1082.998×108 m/s).*k*is the Boltzmann constant (1.380649×10−231.380649×10−23 J/K).*T*is the temperature of the surface (in Kelvin).

## Example Solve

Let’s assume:

*T*=500 K (surface temperature).*Ts*=300 K (surrounding temperature).*λ*=10 μm (wavelength).

Using the formula, we get:

\varepsilon = \frac{{10}}{{0.1}} \times \left( \frac{{e^{\frac{{6.62607015 \times 10^{-34} \times 2.998 \times 10^8}}{{1.380649 \times 10^{-23} \times 10^{-5} \times 500}}}} – 1 \right)^{-1}

After computation, the emissivity value is obtained.

**FAQ’s**

**Q: What is emissivity?**

**A: **Emissivity refers to the efficiency of a surface to emit thermal radiation compared to an ideal emitter, typically a blackbody.

**Q: How does temperature affect emissivity?**

**A:** Emissivity generally increases with temperature, as hotter surfaces emit more radiation.

**Q: What is the importance of emissivity in engineering?**

**A: **Emissivity is crucial in various engineering applications, including heat transfer analysis, thermal imaging, and materials science.

## Conclusion

The emissivity calculator provides a convenient tool for accurately determining the emissivity of a surface, aiding in various scientific and engineering endeavors.