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Questions tagged [thermal-radiation]

The temperature-dependent emission of electromagnetic waves. Combine this tag with the [thermodynamics] tag for a macroscopic view or the [quantum-mechanics] tag for a microscopic explanation.

When to Use this Tag

can be used to discuss the spectrum of electromagnetic radiation as a function of the temperature of a body. Depending on the size of the body and your specific interests, you can combine it with any of , and/or , and others.

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Why does NASA use gold foil on equipment and gold-coated visors?

I've read several websites about equipment covered with gold foil and astronaut helmet visors are coated with gold. However, their explanations are devoid of almost all physics content. Can someone explain the basic concept of why gold foil is so…
Smith
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Explain it to me like I'm a physics grad: Greenhouse Effect

What is the mechanism by which increasing $\rm CO_2$ (or other greenhouse gases) ends up increasing the temperature at (near) the surface of the Earth? Mostly what I'm looking for is a big-picture explanation of how increasing $\rm CO_2$ affects the…
Dave
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Why do metals only glow red, yellow and white and not through the full range of the spectrum?

Why don't metals glow from red to yellow to green to blue etc.? Why only red, then yellow and then white? Shouldn't all wavelengths be emitted one by one as the temperature of the metal increases? If some metals do glow at with different colours,…
Dieblitzen
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Is fire plasma?

Is Fire a Plasma? If not, what is it then? If yes why, don't we teach kids this basic example? UPDATE: I probably meant a regular commonplace fire of the usual temperature. That should simplify the answer.
daniel.sedlacek
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If I stood next to a piece of metal heated to a million degrees, but in a perfect vacuum, would I feel hot?

A friend of mine told me that if you were to stand beside plate of metal that is millions of degrees hot, inside a 100% vacuum, you would not feel its heat. Is this true? I understand the reasoning that there is no air, thus no convection, and…
Peter_Browning
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What are the various physical mechanisms for energy transfer to the photon during blackbody emission?

By conservation of energy, the solid is left in a lower energy state following emission of a photon. Clearly absorption and emission balance at thermal equilibrium, however, thermodynamic equilibrium is a statement of the mean behaviour of the…
Douglas B. Staple
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Why do we feel heat from infrared light but not from shorter wavelengths?

My guess would be that light with a higher energy such as visible or UV would feel hotter, but this is not the case! Is this something to do with human senses or is there a physics explanation?
Giulio Crisanti
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Is the Hawking radiation of a charged black hole thermal?

Suppose you have a Schwarzschild black hole of mass $M$ and angular parameter $a = 0$ (no rotation). Question: is it possible to throw a charge $Q$ at a faster rate than it will be re-radiated? Will the radiation profile be still thermal? If it is…
lurscher
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Does anything in an incandescent bulb actually reach its color temperature (say 2700 K)?

This question is inspired by a question about oven lightbulbs over on the DIY stack. It spawned a lengthy comment discussion about whether an incandescent lightbulb with a color temperature of 2500 K actually has a filament at a temperature of 2500…
Bear
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How does the Earth's center produce heat?

In my understanding, the center of the Earth is hot because of the weight of the its own matter being crushed in on itself because of gravity. We can use water to collect this heat from the Earth and produce electricity with turbines. However, I'd…
rydwolf
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Why don't we use infrared light to heat food?

Why don't we use infrared (IR) or even the far IR just to heat food in a microwave oven instead of, of course, the conventional 2.45 GHz microwaves? Don't people call IR heat waves?
ObsessionWithElectricity
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Could I survive at (or near) absolute zero with a very, very, very thick sweater?

Imagine I'm in an infinitely large vacuum and have a special apparatus built into my body that allows me to breath, eat, pee/poo, etc. and never age. The vacuum is similar to deep space and has no heat source or visible light and is therefore quite…
Behacad
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What would a blackbody sound like?

If a blackbody has a temperature such that its peak frequency was well within our audible range, for example $1\ \mathrm{kHz}$, what would that sound like if we used Planck's law to plot its spectral curve in the frequency domain and performed a…
ayane_m
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Why doesn't the brightness of a bulb change with time?

Household bulbs get alternating current, which means that the voltage of source and current in circuit keep changing with time, which implies that the power supply isn't constant. However, we don't see any changes in brightness of the bulb. Why is…
user181531
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Cooling a satellite

Satellites are isolated systems, the only way for it to transfer body heat to outer space is thermal radiation. There are solar panels, so there is continuous energy flow to inner system. No airflow to transfer the accumulated heat outer space…
inninaro
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