Emissivity 101: What is emissivity?

An essential property in the field of infrared theory is emissivity. In basic terms, emissivity describes how well a target (or material) emits infrared radiation.
In this video, we give a brief introduction to emissivity and its importance in the field of infrared theory. We also discuss calibration sources and how blackbodies are used to calibrate infrared cameras.
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[@kercig2061]

There are very few videos on this subject. So ty!

[@movitherm]

Thank you! We hope to educate folks out there!

[@kercig2061]

Thx for the video!

[@deepakkotnala1658]

To calculate emissivity we have to assume black body of same dimension as object for which energy is we want to calculate for same temperature?

[@emresinandogan6490]

Why you are not taking the absorptivity into an account? The energy will also be absorbed by the surface.

[@Dolcesangue]

Thanks!

[@movitherm]

You bet!

[@songoftherose]

what's the difference between a black hole and a blackbody?

[@movitherm]

Hi! Wow - that is a deep and interesting question!
A black hole and a black body are two very different concepts in astrophysics and thermodynamics.
Black Hole:
A black hole is a region in space where the gravitational pull is so strong that nothing, not even light, can escape from it. It is formed when a massive star collapses under its own gravity, creating a singularity, a point of infinite density at its core, surrounded by an event horizon beyond which nothing can return.
Black holes are characterized by their mass, spin, and charge. They can vary in size from a few times the mass of the sun to millions or even billions of times the sun's mass.
Black holes are not objects that emit radiation; they are defined by their ability to trap everything within their event horizon. They can, however, indirectly affect their surroundings by gravitationally influencing nearby matter and light.
Black Body:
A black body, in the context of thermodynamics and physics, is an idealized object that absorbs all incoming radiation and emits radiation according to Planck's radiation law. It is an ideal absorber and emitter of electromagnetic radiation.
A black body does not have to be a physical object; it can also represent a theoretical concept. In practice, objects like a cavity with a small hole, such as an oven or a star, can closely approximate the behavior of a black body.
The radiation emitted by a black body is characterized by its temperature, and the spectral distribution of this radiation follows Planck's law, which describes how the intensity of radiation varies with wavelength at a given temperature.
In summary, a black hole is a massive, gravitationally collapsed object in space, while a black body is an idealized concept in thermodynamics that perfectly absorbs and emits radiation. They are fundamentally different in nature and have different roles in their respective fields of physics.