Black body radiation Definition and 163 Threads

Wikipedia writes: "Black-body radiation is the type of electromagnetic radiation within or surrounding a body in thermodynamic equilibrium with its environment". Why does it write "thermodynamic equilibrium"? If it is not in a thermodynamic equilibrium, then what changes as far as the absorption...

Heat is a type of energy that is transferable and increases thermal energy. Thermal energy is being released as infrared radiation hence the term heat vision. Does that mean heat is capable of producing so called black body radiation here. Is the infrared radiation caused by the photon emission...

My name is Bradley and I am a first year university student attending Intro to Quantum mechanics lectures but didn't understand... Why the black body radiation curve (unlike the quantized emission seen from atomic spectra), is continuous over all frequencies. I am wondering what exactly gives...

I want to get a half convex lens (thick in the middle, flat on one side). And coat it in thermally and optically reactive transition filters. They are to be segmented so to reduce spread of filtering. This will give a view of the sky with any bright light inhibited at the focus. Next to the...

I want to know, excluding the sun with an appropriate boundary, whether it is possible for the balance of bbr to be positive for outerspace rather than on earth? I am thinking of a half convex with an active polariser across-the outer surface which allows through most radiation below the...

Will a body of given emissivity kept inside a perfect black body start behaving as a perfect black body?

According to the documents I have read, Plank made two changes to Rayleigh-Jeans approach in order to produce an equation that matched the black-body radiation, experimental curves: 1) As a mathematical convenience he assumed that the oscillators in the walls of black-body cavity could only have...

i don't get it. why would a body with temperature give up photons? help please

It is given in my book that the phenomenon of black body radiation can be used to prove the particle nature of light. They have also mentioned that the wavelength-intensity relationship "cannot be explained satisfactorily on the basis of wave theory of light." But why? Thanx in advance...

Hi as far as I have understood: Blackbodies are physicsl objects which absorb electromagnetic waves at ALL frequencies. And the only light they radiate is determined by their temperature which means They don't reflect any light shined on them, they only emit Energy from their temperature...

1. 6. A 100 W light bulb is designed to operate with it’s filament at 2000K. If the filament is a perfect cylindrical Black Body and 2 cm long, i) What must it’s diameter be (3 marks) ii) What will be the wavelength of the intensity peak in its emission. (2 marks) iii) You...

Homework Statement A cylinder of length 0.02m emits 100W and is at 2000K. It is a perfect black body. What is it's diameter? Homework Equations Planck's Law: B(λ,T) = http://en.wikipedia.org/wiki/Planck's_law solid radian = A/r^2 (not sure if needed or not) The Attempt...

$${\rho}({\lambda}) d{\lambda}=E({\lambda})*f({E(\lambda}))*D({\lambda})d{\lambda}$$ $${\rho}({\lambda}) d{\lambda}$$ is density of radiative energy, $$E({\lambda})= k_BT$$ is the energy of an atom vibrate in 3D, $$f({E(\lambda}))=1$$ is the probability distribution. Equals to 1 because we...

Hello! I am hoping someone could help. I have no idea where to start on this, and have been flipping pages for an hour or so trying to figure it out. Find the spectral range Δλ over which a blackbody's intensity B(1/2) is brighter than half of its peak value B(peak). (In other words, find the...

Hi, I've got a simple question regarding the maximum of the spectral energy density in Planck's black body radiation. It turns out that if you calculate which frequency has the most power associated with it (i.e. maximize R(\nu)), then you do it with wavelength as well, and compare, they're not...

why or how does an object emit radiation of different wavelength for a given temperature?

Obtaining the correct black body spectrum is one of the great triumphs of quantum physics. It is also touted as a total failure of classical physics, since with very basic assumptions, namely thermal equilibrium and the validity of Maxwell's equations, one gets the well known divergent...

Hi, I'm trying to understand black body radiation but I have two conflicting descriptions (both reputable sources). Maybe both are true, but I need some clarification please: 1. A black body is a perfect emitter – it will emit equally well at any wavelength. 2. The black body re-radiates...

Homework Statement Much of the of heat lost from a cross-country skier's body is radiated from the head, since it is often uncovered. Treat a head as a 20-cm-diameter, 20-cm-tall cylinder with a flat top. If the surface temperature of a body is 35 C, what is the net rate of heat loss on a...

If a black body is heated to a temperature T (in degrees K), the most intense radiation is at a wavelength lambda (in m), where λ·T = 2.9×10−3m*K. If the burner on your electric stove is at a temperature of 683K (really hot and glowing), find the wavelength of the most intense black body...

Can someone help explain what's going on here? http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/radpow.html#c1 Specifically the part about how radiated power is greater than perpendicular power. I also don't understand why the power is being averaged over the various angles. Doesn't it...

Suppose you have a container with perfectly reflecting walls, containing electromagnetic radiation that is not in equilibrium (i.e. does not have a Planck distribution of energies.) Will photon-photon interactions (QED and/or gravitational) produce a Planckian distribution after a sufficiently...

black body radiation question?? Homework Statement Ina dark room ambient temperature T0, black body is kept at a temperature T. keeping the temperature of the black body constant(at T), sun rays are allowed to fall on the black body through the hole in the roof of the room. assuming that...

I'm looking for a conceptual explanation of a formula in Quantum Mechanics Demystified introduction. They introduce you to the theoretical black body radiation experiment, where demonstrated how a classical approach leads to the ultraviolet catastrophe. In the explanation they have the...

In black body radiation, there are two regions of low intensity. One is at the high frequencies and one is at the low frequencies. I understand that there is lower probability to emit radiation at high frequencies because it requires higher energy than the average thermal energy provided...

If you consider the standard cavity experiment for black body radiation, you know that the number of standing wave modes at higher frequencies is higher than the number of modes at lower frequencies. Therefore, according to classical equipartition theorem, there should be more energy in the...

This is just for grasping the concept of the Black Body curve and the UV catastrophe. I don't understand how ideal Black Bodies work? or how they absorb and re-emit the energy which they absorbed? Also, why does radiation bounce around the walls of a cavity of a Black Body? shouldn't the...

Consider a hollow cuboid with a small hole on one of it's sides(interior surface is mat black).and let this cuboid be in a vacuum.if we allow a light ray to pass trough this small small hole. from which surface would the re radiation occur? Does this happen? the amount of radiations...

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 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...

Homework Statement im at the point where i ve to plot graphs of intensity versus wavelenght of a tungsten lamp for different temperatures.i ve calculated corectly the temperature and the wavelenghts..after that i took Planck s formula to find the corresponding intensity for each wavelenght and...

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...

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

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...

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...

I am looking to prove the relation I=(1/4)cE Where I is the radiation emittance which is the energy emitted by a black body per unit area per unit time and E is the radiation energy density (energy per wavelength summed over all wavelength/frequencies of electromagnetic radiation emitted)...

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...

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...