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

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Black body in thermal equilibrium

In the answer of an exam said that a black body in thermal equilibrium with it's surroundings won't emit any energy, but I don't really understand why. My logic is that every object emits ...
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58 views

How much time would have to pass for a blackbody object at 0.1 K to emit a single infrared photon? [closed]

My understanding is that blackbody radiation occurs on a curve that depends on the temperature of the object - as the temperature increases, the area under the curve increases, and the peak of the ...
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44 views

Why do high altitudes have larger diurnal temperature variation than lower altitudes?

It seems like the lack of atmosphere should not be playing a role in the diurnal temperature variation because that's what makes it colder. Mountains are not that dry, usually.
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329 views

A “bump” in the cooling curve of naphthalene? [closed]

While doing an experiment, I noticed a slight bump in the cooling curve. I have searched for it on the internet and all of the articles say that it is something related to super-cooling. The graph's ...
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What would the RBG color value of an infinitely hot blackbody be?

In other words, what is the limit of the rgb values of color temperature as temperature approaches infinity? Put differently, what is the terminal point of the Planckian locus? Is there an exact value?...
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What causes a black-body radiation curve to be continuous?

The ideal black-body radiation curve (unlike the quantized emission seen from atomic spectra), is continuous over all frequencies. Many objects approximate ideal blackbodies and have radiation curves ...
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294 views

What is the origin of blackbody radiation? [duplicate]

Of course I know what black-body radiation is, like everyone else who has taken a thermal or statistical physics course. But it was recently pointed out to me that one thing that is rarely taught (...
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3k views

Wien's displacement law in frequency domain [duplicate]

When I tried to derive the Wien's displacement law I used Planck's law for blackbody radiation: $I_\nu = \frac{8 \pi \nu^2}{c^3} \frac{h \nu}{e^{h\nu/k_bT}-1}$ Asking for maximum: $\frac{dI_\nu}{d \...
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How much work can we extract from a black hole?

Recently, I've read an article on scientific regarding the possibility of a stairwell into a blackhole (unsurprisingly, it isn't possible). I've found the following question more interesting: ...
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1answer
110 views

Calorimetry - Emitted Joules [closed]

How can one calculate the total amount of emitted joules from an object with a temperature that isn't constant? A great start is this formula: ...
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3answers
125 views

If heat can't be transformed into other forms of entropy, why do hot things radiate electromagnetic waves?

The laws of entropy says entropy can only increase. On the other hand, if I take a hot object, it will naturally convert its heat into EM radiation. How is this possible? Does EM radiation count as ...
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64 views

Are these two writings of Planck's Law the same thing? [duplicate]

I checked one of the other questions on this - and I still seem to have a different equation than they offer (as far as I can tell). I'll use the notation the books used, btw. In one of my reference ...
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What is the difference between thermal and infrared imaging?

Is there any sort of difference between thermal radiation and infrared radiation at least when detected by a camera? What are the differences between the two?
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1answer
1k views

How does the hot cup of tea cool down? [duplicate]

I am not sure about my answer. I think that the cup of tea cools down by the following modes: Radiation between the surface of the tea and the air molecules. Conduction between the tea and the cup ...
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3answers
99 views

The thermal expansion of material

The question is that: they drill a hole in the middle of a metal. Then when this metal is heated, will the hole become larger or smaller? The hole will get bigger, by experiment, but I think that when ...
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28 views

Computing color and brightness of a hot material

Every blackbody color calculator I've managed to find only calculates hue and saturation; they completely ignore brightness, which severely limits their usefulness if you're trying to model the actual ...
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4k views

How many X-rays does a light bulb emit?

I read somewhere that most things1 emits all kinds of radiation, just very few of some kinds. So that made me wondering whether there is a formula to calculate how many X-rays an 100W incandescent ...
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1answer
283 views

An object glows red at around 1000K while a red star is around 3000K. What causes this misalignment in spectra?

According to the H-R diagram, a red star is 3000K, a yellow star is 6000K and a white star 10000K. But a hot metal appears red at 1000K, yellow at 1500K and white at 2000K.(approximately) Why is ...
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158 views

What is the wavelength of a hot metal when its temperature 400 C? [closed]

I would like to know what will be the wavelength of a hot steel which temperature is 400 degree C
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130 views

Second Law of Thermodynamics and heating a blackbody with another blackbody

Given a large blackbody with surface area $A_1$ and temperature $T_1$, let's assume I can use some mirror and lens system to capture all the emitted radiation and transfer this energy to a smaller ...
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90 views

When can we assume a body to behave like a black body?

In an experiment I estimated the temperature of a Tungsten bulb filament measuring the resistance of it, and tried to verify whether the power of the filament is proportional to the fourth power of ...
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1answer
746 views

Is Ronald Ace's “solar trap” patent plausible?

This newspaper article and a few others from last year discussed a patent by independent US inventor Ronald Ace. It's about a kind of absorber for solar thermal energy systems, and it's supposed to ...
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34 views

Is there an acoustic Black Body Radiation?

Imagine a cavity in a infinitely extended solid filled with another type of solid in thermal equilibrium. Are there statistics for phonons equivalent to the Black Body Radiation by Planck?
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299 views

How does an infrared thermometer actually calculate temperature?

I am slightly confused about infrared radiation and the equations related to it. $P = A \epsilon \sigma T^4$ (1) and $B_{\lambda}(\lambda,T) = \frac{2hc^2}{\lambda^5} \frac{1}{e^{\frac{hc}{\lambda ...
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1answer
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Power radiated by the Sun at different locations [closed]

I am wondering can someone help to solve second part which extends first part; The power radiated by the Sun is ${3.9*10^{26}}_{watt}$. The earth orbits the sun in a nearly circular orbit of radius $...
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384 views

Will Neil Armstrong's moon boot marks really last for thousands of years?

This question concerns the residual heat (if any) contained within the Earth's moon. At the time of the Apollo moon landings, it was widely reported that the boot marks left by the astronauts would ...
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351 views

Explain Stefan-Boltzmann Law?

Can someone explain the Stefan-Boltzmann law in an easy-to-understand way?
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52 views

Car Heating due to the sun: comparison of different contributions

Let's imagine that we need to choose a car in order to minimize the Temperature that the inner part of the car will reach after some hours under the sun. We know that two factors (if we suppose that ...
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226 views

Does one square centimenter of the sun core really radiate this amount of energy?

I have been thinking that since the core of the sun maintains its temperature at 15 million degrees Kelvin, then every cubic centimeter of this core is receiving a certain amount of energy to keep it ...
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52 views

Heat transference in my lunch [closed]

Say that I have a hot sandwich and a cool salad, both in functionally-identical plastic containers that provide no effective heat insulation. I need to stack these two containers for ease of carrying,...
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2answers
5k views

Temperature on the surface of the sun calculated with the Stefan-Boltzmann-rule

In a German Wikipedia page, the following calculation for the temperature on the surface of the Sun is made: $\sigma=5.67*10^{-8}\frac{W}{m^2K^4}$ (Stefan-Boltzmann constant) $S = 1367\frac{W}{m^2}$ ...
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43 views

Temperature modelling

I have to find a mathematical model for the temperature vs. time to study the temperature of the environment next to a lamp. This lamp is made off and on on, let's say, a daily basis The lamp is ...
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1answer
123 views

Temperature of planets without atmosphere

I am wondering how come a planet without atmoshhere loses heat in space when the space around it is a vacuum. In my understanding for one object to lose heat it must have contact with another object/...
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162 views

Radiation from home heaters [closed]

My understanding of radiation is energy being emitted from a source. So much radiation would come out of a home gas or oil heater to become dangerous. I'm assuming infrared radiation.
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Classical absorption of radiation

How does electromagnetic radiation get absorbed by an object (like a black body) in the classical regime? In the classical picture, electromagnetic radiation is produced by the movement of charges, ...
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55 views

How to combine contributions of individual type of cone cell sensitivity to get the human luminosity function?

As shown in this figure from some computer vision book: The data of three types of cone spectral responses is pulled down from: http://cvrl.ioo.ucl.ac.uk/cones.htm It is said that the Long, Medium ...
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2 ways to generate electromagnetic wave

According to Maxwell's equations, accelerating charges emit electromagnetic radiation. According to Quantum physics, heating causes electromagnetic radiation too. These 2 radiations, are they ...
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92 views

Is UV catastrophe same as IR catastrophe?

I am currently studying quantum physics from Serwey-jewet. Where in the topic of Planck's law, infrared catastrophe is alternatively used for UV catastrophe while explaining how Plancks constant ...
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How can I find the radiance over a finite range of wavelengths using Planck's Law?

I'm working on a small programming project involving Planck's Law, and I keep getting errors. I'm fairly certain this is due to a misunderstanding of physics on my behalf. Basically, I am trying to ...
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Would wearing clothing that is black on the inside and white on the outside keep you cooler?

The Straight Dope ran an explanation of why nomads often wear black clothing - it absorbs heat better from the body. On the other hand, white clothing reflects sunlight better. Is it possible to get ...
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In theory, Is it possible irradiate a blob of matter -for instance- with microwaves in order to that matter emit more energy than has received?

Suppose that you want coerce a block of matter to lose his energy. I mean thermal energy. This should be done by irradiation of more energy. The final thermal energy should be lower that the original ...
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I don't understand black body radiation graphs

Let's look at the above graph. This black body graph is for the temperature of 5000K. Each temperature has a different black body graph? How am I supposed to read this graph? Do I start from the ...
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Cooling down a container in outer space

If I have two containers filled with very hot water(~210F) with one in outer space and one on earth, which one has a higher rate of cooling initially? Imagine the containers are single wall metal ...
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3answers
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How does the heat of Sun come on Earth when there is no medium?

Sun is the most important source for life on Earth which gives sunlight and heat on Earth. But I was wondering like how does the heat of Sun come on Earth when there is no medium out there in space?
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1answer
341 views

How fast does heat travel via conduction?

I have read this question which seems to ask an identical question, but I'm not sure - it had far too many words I don't understand, let alone the equations. Perhaps someone can answer with a heat-for-...
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3answers
151 views

Different materials have different temperatures?

Why do two materials, under the same weather, have different temperatures? I have a small clue about it. For example, iron and wood supposed under the sun's radiation, and if we touch both of them, ...
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5answers
3k views

Entropy of radiation emitted into space

In several papers I see something equivalent to the following expression for the entropy of radiation given by an astronomical object such as the Sun (assuming the object can be approximated as a ...
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1answer
98 views

Quantization in Black Body Radiation [duplicate]

Why does energy need to be quantized to explain black body radiation? Wouldn't the approximate normal distribution of the kinetic energy of particles at a certain temperature be sufficient, ie. few ...
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382 views

How exactly does wave theory of light fail to explain blackbody radiation? [duplicate]

I don't really understand the reason why wave theory of light fails to explain the blackbody radiation. My textbook says the Planck's quantum theory explains blackbody radiation. It says "If we assume,...
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37 views

Am I very wrong with my grey body calculations?

I'm trying to calculate the maximum heat that an object on the moon can reach with the energy provided from Sunlight. I've got a total power output of the sun per square meter at the distance of the ...