Black body Definition and 155 Threads

What is the proof that the total rate at which radiation is emitted by a black-body radiator is proportional to the fourth power of the temperature? Does this result come from Planck's radiation law? If yes, how?

When objects are heated they produce blackbody radiation which varies with their temperature, and when the electrons in the orbitals of atoms are given energy they produce radiation at specific frequencies known as spectral lines. My question is this. When an object, say a piece of mental is...

Homework Statement Suppose you are inside a black body radiation cavity which is at temperature T. Your job is to measure the radiation field in the frequency interval from 1014 to 89 x1014 Hz. You have a detector to do the job. What should the temperature of the detector (T’) be? Explain...

Homework Statement Write the volume element of d3p as a function of "nu". Assume spherical symmetry in doing this change of variables so write d3p = 4\pip2dp. Homework Equations n(\nu)=\frac{1}{e^{\frac{h \nu}{kT}} -1} \epsilon=\frac{2}{h^3}\int h \nu \cdot n(\nu)d^3p The Attempt...

To derive the blackbody spectrum, we set up the situation by assuming that a cavity is in thermodynamic equilibrium with a heat bath. My questions are: 1) Is the heat bath the black body? 2) Why is it called a blackbody? 3) Why does the cavity have to be in thermal equilibrium with...

Homework Statement To make a long question short, we have the Planck distribution function for a blackbody and the question basically asks to sketch the behavior of this function and explain how one figured these trends. Homework Equations Planck Distribution formula: The...

Hello, looking for a picture of black body radiation from an oven Years ago I had found a nice illustration. An opened hot oven was shown. The pottery inside could hardly be seen. This illustrated what I believe is one of most important aspect of a black body. If is specially useful...

Homework Statement how does Planck's idea of quantization of the energy found in electromagnetic waves solve the problem of black body radiation? Homework Equations N/A The Attempt at a Solution this is what i have said correct me if I am wrong... so plank said that photon has...

In the book "Introduction to the structure of matter" by Brehm and Mullin, page 78. They say "It should be empathized that there is no reason for the peak positions \mu _m and \lambda _m in the respective distributions to be connected by the relation c=\mu \lambda. They are talking about the...

Where can I find a lot of information on it that wasn't meant for a Quantum Physicist? I am pretty sure that once I understand that learning about EMR will be easier.

To make my question simpler, assume that there's a black body at 0K or very close to it (if we can't assume there's a body at 0K). Say I have a monochromatic source of photons which sends 1 photon on the black body. The wavelength of the photon is 500 nm so around green. If I understood...

Homework Statement An evacuated container with volume V and at a temperature T contains black body radiation with an energy density equal to 4\sigmaT4/c I Determine the heat capacity at constant volume of the radiation II Hence show that the entropy of the radiation is given by...

If I'm not mistaken he explained it with the theory that light energy can be released only in integer multiples of a constant times the frequency of the light. How did he come to this conclusion? Was it to do with the fact that the higher the temperature, the higher the frequencies of the light...

Homework Statement What percentage of the Sun’s blackbody radiation spectrum falls into the visible light spectrum (400-700 nm). Where T=5000K Hint: Integrate over frequencies Homework Equations B=2h\nu3c-2 (eh\nu/kT-1)-1 Where \nu is the frequency of the light. The Attempt at a...

Hello, I am trying to revise for my Solar System exam and going through a past paper i have a question relating to something that we don't seem to have covered: "By estimating the energy output of the Sun's corona (in watts), comment on whether can be treated as a blackbody radiator...

Question: A spherical black body is kept at constant temperature thermal equilibrium T and by supplying heat from some source. It is covered by another spherical surface which is also a black body (a very thin surface of radius almost equal to the previous one). Find the temperature at which...

What is box normalizing and why is it important in quantum mechanical problems such as the black body radiation?

Homework Statement A naked person, whose skin area is 1.7 m2, sits in a sauna that has a wall temperature of 61oC. If the person’s skin temperature is 37oC, find the net rate at which the person absorbs heat by radiative transfer (assume an emissivity e of 1). How much liquid must the...

Hi all -- I had a question about the Planck black body / Johnson-Nyquist resistor temperature formula: \[ E_{\nu}^{2}d\nu=\frac{4R_{\nu}hd\nu}{e^{h\nu/kT}-1}\] I'm just wondering why the formula has $ exp(h\nu/kT)-1$ in the denominator? I would have expected $ exp(h\nu/kT)+1$ as...

Hey In several books, the derivation of black body radiation is done by considering the energy density inside a cavity surrounded by walls in a certain temperature. The derivation is described as one of the first steps in quantum mechanics, where all considerations are purely classical but...

Is this black body radiation considered light? PS: Sorry, I spelt emit wrong:(

Hi all: I am confused about one question. When we detect signal from human brain using coil in Nuclear Magnetic Resonance, two source contribute noise to our signal. One is coil itself. The other is human brain. Why can we think the noise from human brain is white noise? Can we compare the...

Hello! I am looking for books about black body in motion but i can't find any in Google. So, does anyone know something about it and let me know? Just even the address of where i can find it is enough. Actually, the black body that i know is the one which absorbs all incident light...

My apologies if I am posting this in the wrong forum, and if this question has already been asked. This is my first post. First off: I'm a first-year undergraduate student. My program is Philosophy of Physics. I am trying to understand (more fully) black body radiation. I am having trouble...

if something is black in color, that means it doesn't reflect light(photon)? where do this light got? also for black hole why people say that the gravity of black hole is so strong the light cannot escape? Is it means that gravity can affect em wave?Thank you~ Of topic problem...

Is a black hole considered a black body?

Homework Statement The total radiation emitted by a certain star is a factor 16 times that of a second star of equal size. Calculate the ratio between the temperatures of the star. Homework Equations lamda x T = 2.90x10^-3 The Attempt at a Solution 16I = I Therefore, Wiens Displacement law...

Homework Statement In an experiment to measure photon statistics of thermal light, the radiation from a black-body source is filtered with an interference filter of bandwidth 0.1 nm centered at 500 nm, and allowed to fall on a photon-counting detector. Calculate the number of modes incident on...

Plank’s Law which descibes black body radiation is derived from first principles so I am not quite sure why it is called a Law. http://en.wikipedia.org/wiki/Plank_law"

Find\int\frac{x^3}{e^x-1} evaluated between zero and infinitum. I got...

Homework Statement Assume that the radiation emitted from the Sun moves radially outward from the Sun and that no radiation is absorbed between the Sun and Earth. How much energy in the form of radiation will fall per second on an area of 1 m2 on Earth, if that area is perpendicular to the...

***** SHEETS two ideally black of the area 1:5 mETER SQUARE are located opposite of each other in vacuum. The first SHEET P1 has the FIXED temperature T1 = 0o C, the second SHEET P2 has the fIXED temperature T2 = 100o C. Now an additional black panel PM of the same size is brought between the...

I think it has been asked a lot of times and explained a lot of times, but as I've never seen the answer I post my question here. Why does a black body never becomes green when it is heated? It pass from infrarred to red, orange, yellow but instead of passing to green, it then passes by...

Hi, I feel extremely stupid for having to have this explained to me, but I am really confused by it. I recently encounter a proof of the fact that the brightness (energy/(time x area x solid angle x frequency)) of a black body can only depend on its temperature, not the properties of the...

# Hi guys! One question is troubling me a lot. It is know fact that a hollow metallic enclosure with a small hole is a perfect black body. When electromagnetic waves of any frequency are incident on the hole, it is completely absorbed after a number of reflections. So, the condition for...

taking a lump of coal as an approximation of a black body, what is the explanation for the phenomenon of the emitted light changing colour from red to white when it is heated, ie the emitted quanta themselves changing, rather than simply more being released.

If I make a ball out of calcium; drill a little hole in it; then heat it up in a suitable [vacuum] environment; I see black body radiation thru the little hole, right? At least up to the melting point of calcium ?? I mean, black body radiation is independent of material, right ? Yet the...

The blackbody temperature of Earth is supposed to be -18C or 255K. This can be derived by reworking Stefan Boltzmann law to: TK = (S*(1-a)/4*rho) ^0,25 http://www.lwr.kth.se/Grundutbildning/1B1292/Compendium_online/ch05s02s01.html in which S is solar influx, we use 1367 w/m2 a is...

Im working on designing a non contact thermal instrument. Need to estimate how much current I'll get from the photodiode. First background: I'm working from Planck's law and Stephan's law. The temperature of my target will be between 1250 and 1750K. From Stephan's law I've worked out this...

I came across a formula that gives radiant energy density as 4 * sigma * T^4 / c. I am trying to figure out how this formula follows from Stefan-Boltzmann law. Shouldn't it be 4*pi instead of just 4? I am also wondering why one can just stick in c. TIA

I was looking over the calculation leading to the thermal average number of photons s in a mode of frequency w in a black body. The approach was pretty straightfoward: Calculate the partition function Z based on quantized energies of a harmonic oscillator, then use this to calculate: <s> \ = \...

In reading about the “Ultraviolet Catastrophe” in dealing with black body radiation, my book says that at the ultraviolet frequencies and beyond, the Rayleigh-Jean equation for the energy density of the radiation would be infinite (and thus a catastrophe). If this is the Rayleign-Jeans...

Homework Statement 1)The peak emission from a black body at a certain temperature occurs at a wavelength of 9000 Angstrom. On increasing its temperature the total radiation emitted is increased 81 times. At the initial temperature, when the peak radiation from the black body is incident on a...

Hi all, I hope everyone is well and that life is treating you all good. I am going to be honest with my question and say that I have not tried to do it myself yet. I, unfortunately, do not have time now to try and then repost so I do hope you will all forgive me for just stating a...

Sir, A polished metal plate with a rough black spot on it is heated to about 1400 Kelvin and quickly taken into a dark room. It is said that the black spot will appear brighter than the plate. Is it because the black spot is a perfect black body and hence is a better absorber of heat than...

Hi, I found one very interesting physics problem but I have no idea how to solve it. Lets say we have a star with radius R and the surface temperature T. Now we wish to know, what is the ratio between the total power output of the star and the power that the distant planet receives from...

You heat an ideal material (solid, liquid, gas) and it emits electromagnetic radiation, with a spectral energy distribution (SED) following that of a "black body", per Planck. You heat a homogeneous real material (a lump of iron, a body of water, some hydrogen; things like dust with a wide...

can i ask ... how could Planck's idea of quantised energy explain the ultraviolet catastrophe? WHAT is being quantised? the oscillator atoms of the blackbody cavity? or? thanks

Hi i was just wondering you when black bodies emit all spectrum of electromagnetic radiation. Now are atmosphere absorbs a particular part, therefore the peak wavelength and temperature appear to be different according to the rules of wiens law. Now does Earth atmosphere absorb Shorter...

If the sun at temperature 6000K emits onto an asteroid 350million km away, what is the temperature of the asteroid assuming it is a black body? Any suggestions how to go about this please? :confused: :confused: