All Questions
Tagged with thermal-radiation frequency
54 questions
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Planck's Law frequency vs wavelength [duplicate]
I was plotting planck's law today and attempted two different implementations. I took both from this table on Wikipedia. They are:
In terms of wavelength:
$$
B_{\lambda }(\lambda ,T)={\frac {2hc^{...
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2
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120
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Differential form of Planck's Distribution Law interpretation
So I didn't encounter differentials that often until now, I was taught that the seperate parts of $dy/dx$ for example are not supposed to have any sort of independent existence - ok.
(Calculus, 4th ...
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Wavelength and frequency of the peak of the black body radiation [duplicate]
Why does the product of the peak wavelength and the peak frequency of Planck's black body radiation not equal to the speed of light?
$$λ_{\mathrm{max}}=\frac{hc}{4.97\mathrm{kT}},$$ while $$ν_{\mathrm{...
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2
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Does sunlight have a modulation frequency?
By frequency, I don't mean electromagnetic frequency, I mean modulation frequency. For example, I can put a PWM square wave on an LED at some frequency, which I can detect with a photodiode and a ...
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Jumps between energy states of harmonic oscillators
I have recently read that in perfect harmonic oscillators to go up or down in energy state you have to go, using the simile of a staircase, step by step, emitting or absorbing a photon of energy $E=\...
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What were the laws in classical physics that led to prediction that black body will emit infinite energy at high radiation and how?
I have tried to search a lot about the laws that predicted this behaviour of black body. But haven't really found out. And the ones I found like equipartition theorem, i find them contradicting with ...
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How efficiency works for objects
Imagine, there is an object(objA) which is not a black body. But this object is a kind of object that does not reflect any energy(light). It can only absorb and transmit.
We know that blackbody emits ...
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What determines the particular frequency of infrared any given object emits?
Infrared (IR) includes EM waves between 780nm and 1mm in wavelength. (Source) As an object gets hotter, it emits a greater amplitude of infrared. What determines the particular frequency(s) of IR an ...
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1
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Is the Drapers point inaccurate?
Is the Drapers point faulty since an oven glows visibly red without it actually reaching Drapers point? When the Drapers point blackbody radiation frequency is calculated by Wien's law it results ...
user348071
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6
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Do all objects at the same temperature glow the same color?
Does Kirchhoff's law for heat radiation imply that all objects at the same temperature will glow the same color?
In other words, if a piece of molten iron glows the same color as my body, which ...
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Converting between $F_{\nu}$ and $F_{\lambda}$ spectral density
In papers, spectral energy distributions are given either in $F_\nu$, $\nu F_\nu$, $F_\lambda$ or $\lambda F_\lambda$.
$F_\nu$ has units of Janskys, for example.
Is there a clear explanation online I ...
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Why is the energy emitted by a black body low at higher frequencies? [duplicate]
In the blackbody radiation spectrum, we clearly see that energy radiated is very less at higher frequencies.
"At high frequencies the amount of energy in a quantum, $hf$, is so large that the ...
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Is the temperature of light affected by color filters?
This video demonstrates how varying color filters alter the energy of photoelectrons emitted from a light source:
https://www.youtube.com/watch?v=kcSYV8bJox8
But I am confused by what these different ...
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2
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What is the wavelength of white light? [closed]
Does white light have a wavelength, and I know that the sun emits white light, but the atmosphere makes it refract to make it appear yellow to us. Do all the stars in the universe emit white light?
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Planck's law question
I was reading Wikipedia article about Planck's Law and I wanted to make the same graph as here.
I took this equation
$$ B(\nu,T)=\frac{2h\nu^3}{c^2}\frac{1}{e^{\frac{h\nu}{kT}}-1}$$
but I got ...
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3
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Why does the maximum of Planck's distribution function depend on how it is plotted? [duplicate]
I was reading Fundamentals of Atmospheric Radiation by Craig F. Bohren and Eugene E. Clothiaux and in page 20-23 they discuss the idea that the maximum of the Planck's distribution varies depending on ...
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Why does Wien's law not work for lower frequencies?
I just found out Wien's law is only a good approximation at high frequencies/small wavelengths but am not sure why. Does anyone mind explaining?
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Discrepancy of $4π/c$ for radiated intensity in a blackbody radiation
Plancks radiation law is sometimes given as
$B(\nu, T)=\frac{8π h \nu^{3}}{c^{3}} \frac{1}{e^{\frac{h \nu}{k_{\mathrm{B}} T}}-1}$ as is shown in the plot
But Wikipedia says:
...the spectral radiance ...
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5
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What exactly was the "classical model" of black-body radiation, and what assumption about it made it wrong?
While studying black-body radiation, I saw that most of the textbooks and videos I watched mentioned that there was a contradiction between the classical model of black body radiation and ...
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Where does the minus sign go when deriving the Stefan-Boltzmann Constant?
When deriving the stefan boltzmann law from planks law. You may make a substitution (http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan2.html). This substitution will lead to a stray minus sign ...
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161
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Why can we equate these two integrals related to blackbody radiation?
I was reading this Wikipedia article which describes how Planck’s Law of blackbody radiation is derived. Letting $B(v,T)$ represent the energy emitted at frequency $v$ and temperature $T$, the article ...
2
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2
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How did Max Planck solve the black body problem?
I have read some books and references about quantum mechanics and black body radiation but still I didn't understand that what is the black body in fact and how did Planck solve the problem of black ...
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Wavelength and Wavenumber not matching from Spectracalc [duplicate]
When I use Spectracalc.com to calculate the peak wavelength at 500 Kelvin, I am told the peak is at 5.79551 µm. When I switch the calculation result to wavenumber the peak is said to be at 980.506 cm-...
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Spectrum range of black body radiation [duplicate]
Why does a black body emit at all frequencies at thermal equilibrium?
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Planck's law - spectral radiance per wavelength, wikipedia article [duplicate]
I am looking at the wikipedia article of the Planck's law. Is the second formula correct?
$$
B_\lambda (\lambda, T) = \frac{2hc^2}{\lambda^5}\frac{1}{e^\frac{hc}{\lambda k_B T} -1}
$$
If $f = \frac{c}...
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1
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Planck theory of discrete energy of photons and electromagnetic spectrum
Planck said that "energy of photon is quantized. That means energy of a photon cannot be any random value but a certain values only".
If this is true how electromagnetic spectrum is continuous. For ...
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1
answer
215
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Frequency and wavelength of thermal radiation [duplicate]
Why for a given temperature these forms of Wien's law implies a different maximal wavelength?
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1
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788
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Black body radiation curve
See images about black-body radiation.
How does Planck's quantum theory explain the low intensity of radiation for high frequencies?
I.e why does the black body curve become lower at the high ...
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Inconsistency in two equations for Planck law given by professor
I know there are a variety of questions about this topic but I have been searching the internet for a long time and couldn't find a proper answer. The question is simple:
I saw the following formula ...
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What does 'per unit frequency' refer to?
We were discussing Kirchoff's theorem on blackbody radiation in class today and the equation was: $$e_{f}= J(f,T)$$
$e_f$ was defined as power per unit area per unit frequency.
What does per unit ...
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2
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120
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Relationship between Planck's law and absorbed frequencies
What is the relationship between the frequencies of radiation absorbed by a material and those emitted? I know that Planck's law tells us the spectral radiance, but how does this map to those ...
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2
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Do photons exist at all possible wavelengths? [duplicate]
My question refers to Photon flux spectrum diagrams.
The diagram shows the number of photons at different wavelengths. My question is whether the graph is granular or continuous. Do photons exist at ...
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Why do we take the derivative of the number of modes with respect to frequency (Rayleigh-Jeans)
Source: http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/rayj.html
We arrive at this result:
$$N(\nu)=\frac{4}{3}\frac{\pi L^3\nu^3}{c^3}.$$
So now we have a function representing the number of ...
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633
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Planck equation in terms of frequency [duplicate]
Given $$u (\lambda) d\lambda = \frac{8 \pi hc \lambda ^{-5}}{e^{\frac {hc}{\lambda k t}}-1}d\lambda,$$ I want to convert this into frequency form $u(\nu)d \nu$. Basically, I want to covert the amount ...
user206026
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1
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What is the difference between Wien's Displacement Law for peak frequency vs peak wavelength? [duplicate]
While doing research for a high school report I came across the fact that WDL actually has two forms, one for peak frequency and one for peak wavelength, and that these two forms are not the same and ...
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3
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Peaks different in wavelength and frequency space [duplicate]
According to high-school physics, light frequency and wavelength are inversely proportional, and their product is the speed of light. But when discussing spectral power, somehow sunlight peaks ...
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Mechanism for light generation
Is all observable light caused by electrons dropping to a lower discrete energy level while bound in an atom? If so, how can a continuum of frequencies be generated? Is the thermal radiation ...
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Planck's Form of Wien's Distribution Law
Can anyone explain how Wien's distribution law seen in Wien's original "On the Division of Energy in the Emission-Spectrum of a Black Body":
$$ \phi_\lambda = \frac{C}{\lambda^5} e^{-\frac{c}{\lambda ...
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An ideal black body emitter will emit all wavelengths of radiation, but this requires infinite energy. How is this possible?
I read that at a particular temperature, all black bodies emitted all wavelengths of electromagnetic energy but at different intensifies. This would require infinite energy and therefore violates the ...
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Planck's law: $B_\nu (\nu, T)$ to $B_\lambda (\lambda, T)$ [duplicate]
Wikipedia says that Planck's law is:
$$B_\nu (\nu, T) = \frac{2h\nu^3}{c^2}\times \frac{1}{e^{h\nu /(k_BT)} - 1}$$
So, to convert this to wavelength, I substituted $\nu = \frac{c}{\lambda}$ which ...
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What is ultraviolet catastrophe in laymans terms?
From what I understand, ultraviolet catastrophe means that at that time scientists believed that for energy to be higher the frequency should be higher. But frequency is higher in case of ultraviolet ...
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Black Bodies, why is $\nu_{max}\neq {c}/\lambda_{max}$? [duplicate]
I am trying to find Wien's law from Planck's equation but instead of $\lambda$ I am finding frequency.
I found it:
$$\nu_{max} = \frac{(2.82)k_bT}{h}.$$
The following question asks: Why $\nu_{max}\...
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Energy and colours of the stars
We know that stars have different colours because they have different energy. So blue stars have a lot of energy because the blues's frequency is very high $E = h\nu$. The colour of the star is its ...
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Blackbody Radiation -- Minus Sign Popping Up When Deriving Rayleigh-Jeans Formula
I saw this question: Trouble in deriving the Rayleigh-Jeans formula from the steps shown on HyperPhysics site, but I don't consider it answered, so I'd like to dwell a little more into it.
After ...
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Trouble in deriving the Rayleigh-Jeans formula from the steps shown on HyperPhysics site
Hi I am very new to this aspect of physics and I am having trouble with the derivation of the Rayleigh-Jeans from the steps shown at the hyperphysics web site. I have emailed Dr. Rod Nave who is ...
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Can I convert the visible light into another form of electromagetic light form?
can I convert the visible light form into another form of electromagnetic light? actually I want to make a device which convert the objects which are visible to the human eye into invisible as a part ...
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How did Planck derive his formula $E=hf$?
Some time ago I asked my quantum physics lecturer the question:
How did Planck derive his formula, the Planck–Einstein relation
$$E=hf$$
with constant of proportionality $h$, the Planck constant.
I ...
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1
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711
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How can Wien's Displacement Law be 'changed' to a version for frequency?
Wien's Displacement Law stated that for a blackbody emitting radiation,
$$\lambda_{max}=\dfrac{1}{T}$$
where $T$ is the temperature of the body and $\lambda_{max}$ is the maximum wavelength of ...
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1
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Frequency-averaged (gray) radiative transfer
The equation for radiative transfer is
$$
\omega \cdot \nabla I = \kappa(B - I)
$$
where $I$ is the intensity of radiation, $\omega$ is the ray direction, $\kappa$ the absorption coefficient, $B$ the ...
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Why don't the derivatives of the blackbody spectrum over frequency and wavelength match?
The question is:
The radiation emitted by a black body can be represented either by the energy distribution over the wavelength or by that over the frequency. In the first case the maximum energy ...
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