1
vote
2answers
39 views

Internal energy and photon absorption

I just wish to confirm whether my understanding is correct. I know that photon absorption/emission brings about quantised changes in electron energy levels. Photons (infrared) also interact with ...
3
votes
2answers
92 views

Radiation emission and absorption

Any object can emit and absorb radiation and the power of emission can be represented by the Stefan-Boltzmann law: $$P=A\epsilon\sigma T^4$$ In many texts the net power radiated is the difference ...
1
vote
2answers
58 views

EM Radiation and Heat

If there is EM radiation, will there always be a heat exchange between the wave and its surroundings? If you have an extremely energy-efficient light bulb that converts ALL the energy it receives into ...
0
votes
0answers
20 views

Building a magnetron powered steamer

I am wanting to build a microwave powered steamer for a reverse engineering project in university. I've read up some on this and know that its not as efficient as a heating element. I'm curious about ...
0
votes
3answers
2k views

Why does a human body only emit infra red radiation and not other types of electromagnetic radiation?

What causes humans to emit infra red radiation and why don't we also emit other types of electromagnetic radiation such as ultra violet or microwave? Sunlight contains UV and our body takes it in, but ...
0
votes
1answer
78 views

How does a MRI use 20.1kW yet creates over 204K BTU/h? [closed]

I've been reading through a manual about MRI operating procedures for a large healthcare provider. The manual (written by Siemens) states that the MRI machines use 9kW in stand-by mode and 20.1kW ...
3
votes
3answers
1k views

Temperature behavior over time of black or white cars in hot, sunny regions

How does the color of a car influence its inner temperature change over time when parked outside in windless, hot and sunny regions? I know what's the common idea about that: black cars are supposed ...
0
votes
1answer
48 views

Why does black get heated the most? [duplicate]

I found out black heats up the most and white the least, as I expected. The question I had is that despite black reflecting all the wavelengths of the visible spectrum, and hence giving the black ...
0
votes
2answers
152 views

What would give us more heat ? infrared or microwaves?

As we know that our body is made up mostly of water and the frequency of vibration of water molecules matches that of microwaves which is the working principle of microwave ovens. When we come in ...
-1
votes
1answer
131 views

How light causes increase in temperature

Temperature is the measure of movements of atoms. So if something is said to have high temperature it means that its atoms are moving fast or have high KE energy. There are basically two ways heat ...
1
vote
2answers
130 views

Max temperature that can be obtained from radiation source when nonlinear interaction with matter is important?

Using a black body radiation as furnace it is usually said that the max achievable $T$ is limited to the T of the source. So a source of 3000K can not be used to heat a body above 3000K. A long ...
-2
votes
3answers
212 views

How “things” radiate electromagnetic radiation? [closed]

How things radiate electromagnetic radiation? I don't ask why they radiate (higher temperature than 0K) but how they radiate this electromagnetic waves?
2
votes
1answer
323 views

How much does sunlight affect inside temperature?

Suppose we have a $3\cdot 3\cdot 3\,m^3$ room of which one side is glass. And suppose that the other 5 sides have no effect on temperature (super isolation). We know from physics how to calculate ...
19
votes
6answers
2k views

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 ...
0
votes
2answers
407 views

What is the ion drag mechanism in dielectric heating?

While reading about dielectric heating on Wikipedia, I read about the ion drag mechanism but there wasn't enough information about. I know there is another Phys.SE question talking about the ion drag ...
2
votes
1answer
110 views

Could we really charge metal plates using microwaves?

While skimming through Dielectric heating, I read that they use microwaves to charge the plates. How do they do that?
2
votes
2answers
1k views

Why did the microwave oven only heat my coffe half as much as expected?

A sticker on my microwave oven states its output effect to be 750W, which is 180 calories per second. This means that heating 250g of water by one degree celsius would take 250/180 = 1.4s. Now, my ...
6
votes
1answer
636 views

Microwave oven + water: dielectric heating or ion drag?

When you place a water or food in a microwave oven, it heats. Which process commits more energy to that: dielectric heating, or ion drag i.e. resistive heating? AFAIK, in distilled water (which is a ...
2
votes
2answers
3k views

Microwaves vs Gas or Electric Coil heating of a water boiler in a typical household

Wouldn't it be more energy efficient and or safe to use microwaves to heat our home's water boiler instead of using dangerous gas or hot electric coils that could catch other things on fire? I'm kinda ...
3
votes
5answers
679 views

Should I cook two pieces of Canadian Bacon twice as long as one in a microwave?

It will probably depend on the size of the pieces... but at what point should I stop assuming a linear relationship? I was prompted to ask in a previous question.
5
votes
1answer
3k views

Why are lasers inefficient?

Why are lasers inefficient? Is it because of the heat lost during lasing? Why couldn't there be thermocouples or turbines in parts of the cooling circuits to extract something out of that heat?
4
votes
2answers
157 views

Solar chamber trapped light

Was wondering if trapping light in a reflective chamber could heat rods sufficiently enough to heat water? Trying to think of new ways in which we can utilise solar energy.
0
votes
3answers
884 views

Does opening or closing the window in a non-AC car in the summer affect how much heat is felt inside?

This will perhaps look like a very basic and trivial question. But I find it confusing. As an experience, when you are travelling in non-AC car in summer, have people felt if putting on or putting off ...
3
votes
2answers
320 views

How might a resonant antenna and black body radiation interact?

How does an antenna behave when it is cooled so that its black-body radiation is emitting energy at its resonant frequency? Edit: To clarify, its not how they're related in general, but how might ...
6
votes
3answers
8k views

Why do lightbulbs continue to glow after the light is turned off?

I've noticed that whenever I turn the lamp off in my room at night, the lightbulb seems to continue to glow for a minute or so after that. It's not bright though; the only way I even notice it is if ...