## Black Body? [ENDORSED]

(Wien's law: $T\lambda _{max}=\frac{1}{5}C_{2}$ )

Daniel Rivas 3L
Posts: 32
Joined: Fri Sep 29, 2017 7:07 am

### Black Body?

I was just wondering if someone can explain what a black body is to me? Like is it just a thing that is extremely hot? And why is it called a black body if it is usually a glowing white object?

Alex Kashou
Posts: 38
Joined: Fri Sep 29, 2017 7:07 am

### Re: Black Body?

A black body is any object that can absorb any incoming light. It is emits thermal heat due to its high absorption rate. However, if it gets too hot it starts to emit light (glow) from increased amounts of thermal radiation. Thus, all you really need to know is that it is a black body that can absorb any incoming light unlike other objects (typically tested with metals).

Ramya Lakkaraju 1B
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Joined: Fri Sep 29, 2017 7:03 am

### Re: Black Body?  [ENDORSED]

The term black body came about since these objects appear black in color at room temperature. They absorb all light and do not reflect any light.

Posts: 32
Joined: Fri Apr 06, 2018 11:02 am

### Re: Black Body?

When you say that black bodies absorb all light, do you mean all light in the visible spectrum, or the entire electromagnetic spectrum?

Liliana Rosales 1E
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Joined: Wed Nov 15, 2017 3:03 am

### Re: Black Body?

I believe black bodies absorb the entire electromagnetic spectrum not just the visible spectrum.

Mei Blundell_1J
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### Re: Black Body?

Fun fact related to this topic: the Sun is a really efficient black body.

Sarai Viveros 1K
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Joined: Mon Apr 09, 2018 1:40 pm

### Re: Black Body?

Could you explain how the sun is a black body?

Shimran Kumar 1C
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Joined: Fri Apr 06, 2018 11:03 am

### Re: Black Body?

So as the second post under this topic explains, black bodies absorb all light in the electromagnetic spectrum and emit thermal radiation. However, when they get too hot, they emit light.

The sun follows this definition. The sun is very hot, so it emits light. As large stars cool down and die, they can become black holes. Black holes are known for absorbing everything. Thus, suns/stars are black bodies.

Gabi Landes 1-H
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Joined: Thu Feb 22, 2018 3:00 am

### Re: Black Body?

Liliana Rosales 1E wrote:I believe black bodies absorb the entire electromagnetic spectrum not just the visible spectrum.

They do! A black body is an object that absorbs all radiation falling on it, at all wavelengths.

Vienna Cimetta 1L
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Joined: Thu Feb 01, 2018 3:01 am

### Re: Black Body?

Do you guys think we would be asked any questions on this topic? Or is it just another concept to know for future reference

Posts: 40
Joined: Fri Apr 06, 2018 11:02 am

### Re: Black Body?

I had a similar question to this one. I was curious how when wearing a black shirt on a hot day absorbs more heat.

Chem_Mod
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### Re: Black Body?

Please see Dr. Lavelle's class website for more information regarding test 2. He pointed this out during Friday's lecture to the class.
https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=18&t=30872

vivianndo_1L
Posts: 30
Joined: Fri Apr 06, 2018 11:02 am

### Re: Black Body?

Could someone please explain the relationship between the ultraviolet catastrophe and black bodies then?

Jamie Reniva 1J
Posts: 14
Joined: Wed Nov 15, 2017 3:00 am

### Re: Black Body?

Why is it called black body?