# Blackbody radiation and Planck's distribution

• Pachito
In summary, physics books discuss blackbody radiation as a phenomenon where any heated object emits continuous electromagnetic radiation dependent solely on temperature. Planck's distribution, which is based on discretization of energy states, accurately describes this phenomenon. However, there is a flaw in assuming that this applies to gases such as hydrogen. While gases can still approximate a blackbody at certain temperatures, the approximation breaks down when the temperature is high enough to excite the ionization spectrum of the gas. Despite this, the sun, a gaseous object, still exhibits characteristics of a blackbody.
Pachito
physics books on the topic of blackbody radiation say that any given object when heated will emit a continuous electromagnetic radiation which depends only on temperature. Planck's distribution based on discretization of energy states accurately describes this phenomenon.
But is this true?
If I put some hydrogen gas in a container and heat it up, will not it emit light at specific frequencies and not continuously?
Thanks

There is a small flaw in your reasoning: The classical 'black body' radiator is a solid substance. Hydrogen gas, or any other gas, is not a solid body.

SteamKing said:
There is a small flaw in your reasoning: The classical 'black body' radiator is a solid substance. Hydrogen gas, or any other gas, is not a solid body.

That's not quite correct. The assumption that leads to the blackbody spectrum is just that you have an (approximate) continuum of quantum states over the range of the energies that can be significantly excited by the thermal environment. A gas can be a perfectly fine approximate blackbody over a range of temperatures. It's when the temperature gets into the range where you can excite the ionization spectrum of the gas (which can be VERY noncontinuous) that the blackbody approximation breaks down. But even then the sun is a pretty good blackbody, and it's a gas.

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## FAQ: Blackbody radiation and Planck's distribution

Blackbody radiation refers to the electromagnetic radiation emitted by a perfect blackbody, which is an object that absorbs all radiation incident upon it and also emits the maximum amount of radiation possible at a given temperature. This radiation is continuous and follows a specific distribution, known as Planck's distribution.

## Who is Max Planck and what is his contribution to blackbody radiation?

Max Planck was a German physicist who first introduced the concept of quantization, which is the idea that energy can only exist in discrete packets or "quanta". He also developed the Planck's law, which describes the spectral energy density of blackbody radiation at a given temperature. This law is the foundation of modern quantum physics.

## What is Planck's distribution?

Planck's distribution, also known as the blackbody radiation curve, is a mathematical function that describes the distribution of energy emitted by a blackbody at various wavelengths. It is a continuous curve that peaks at a specific wavelength, depending on the temperature of the blackbody.

## How does temperature affect the blackbody radiation curve?

The temperature of a blackbody directly affects the shape and intensity of the blackbody radiation curve. As the temperature increases, the curve shifts towards shorter wavelengths and the peak of the curve becomes more intense. This is known as Wien's displacement law and is a key concept in understanding the behavior of blackbody radiation.

## How is blackbody radiation important in understanding the universe?

Blackbody radiation is a fundamental concept in physics and has many applications in understanding the universe. It is used to study the composition and temperature of stars and other celestial bodies, as well as to explain the cosmic microwave background radiation, which is believed to be a remnant of the Big Bang. Blackbody radiation also plays a crucial role in modern technologies such as infrared cameras and thermal imaging devices.

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