Black body Definition and 155 Threads

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...

Hi, I am trying to implement a low tech, quick "check" source for our radiation thermometers to ensure they are in good working order between calibrations again a calibrated black body radiation source. My idea was to use an integrating sphere with an incandescent lamp as a source. Then two...

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...

Homework Statement A black body absorbs all incident electromagnetic radiation, including visible light which has wavelengths from 380nm to 750nm. IR radiation has wavelengths that are so long they are measured in microns. That suggests that visible light has a higher frequency than IR, and...

I know that a black body is an idealized body that absorbs all the incident EM radiation. And I also know that the BB emits a spectrum of thermal radiation that depends on its temperature. What I cannot understand is the re-emission. For what I've read, when in thermal equilibrium, a BB absorbs...

Homework Statement Find the surface temperature of a small planet having circular orbit around the sun with time period T,assuming sun and planet to be black bodies. Take radius of sun = R, its mass = M and its surface temperature as ##\theta_0##. Homework Equations ##P=eA\sigma T^4## Total...

My question is, given that the Sun is composed almost entirely of just hydrogen and helium, why is the spectrum from it continuous and not an emission line spectrum? This applies to other stars as well. There are other elements of course present in the Sun, but they are present in very small...

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

Homework Statement If a black blob and a white blob of the same size are each heated to 3000 Kelvin, the black blob will glow brighter.Question 11 options: True False Homework Equations none The Attempt at a Solution white because it reflects all incident rays?

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 understand photon absorption/emission by electrons in atoms, that transition them between energy levels, producing sharp spectral lines. However, I am having difficulty understanding photon absorption/emission by the vibrational and rotational modes of molecules, with respect to black body...

Hi all! I would be interested in paints that show very high absorptivity/emissivity and that can withstand high temperatures (ideally above 1000°C) and used in vacuum. Do you have any commercial suggestions? Thank you!

Homework Statement The power delivered in narrow spectrum range near 10 µm from black body source with temperature 1000 K is 10 µW. Not Solved a) What power would be delivered in narrow spectrum range near 1 µm? Solved b) At what wavelength the power delivered takes its maximum? c) Find this...

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

This may seem like a strange question, I'm trying to differentiate between the spectra from a plasma and the spectra from a black body, is there a difference? I'm thinking the spectrum from a plasma would be that of bremstrahhlung as it is ions flying everywhere, so it would not be possible...

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...

I'm having the hardest time understanding Black bodies. I have a lot of questions about them so I can't write all of them, instead I'll just start with : Why are stars considered black bodies?

Hello I am wondering, does a black body release energy as heat, or does it only absorb all energy that basically comes into contact with it? Thanks

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?

I was wondering about the spectral radiancy curve of a black body. How does the spectral radiancy of any other body looks like. I have seen one among many possibilities: http://www.giss.nasa.gov/research/briefs/schmidt_05/ Q 1. But i was thinking that for a general body (not a black body)...

Recently on an aquarium related forum, I called out someone for making what I considered to be an outlandish claim and I was supported by several others. However I wish to get the opinion and/or facts explained by someone from a purely scientific standpoint. This has to do with the heat...

what is the shortest and longest wavelenght that has experimentally observed for a black body? Additoinally what are the theoretical limits? I know it's a hard one,

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...

When we see the black body radiation graphic (intensity vs frequency), we could say the spectrum emitted by a black body is not discrete, it's continuous (as all the frequencies are emitted). How can this be possible? If we have a black body made of Sodium, wouldn't the spectrum have only...

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...

When a black body is heated the colors listed are IR, red, orange, yellow, white, blue-white, UV. Why doesn't a black body radiate all colors when heated: Red Orange Yellow Green Blue Indigo Violet? And why not shades of these colors?

Would an ideal black body be visible to us? What about Ferry's black body? How close was it to an ideal black body?

So as I understand a perfect black body in physics would be one that would absorbs all the radiation wavelengts coming onto it ad let nothing out? If sun is a black body, we all know it emits both visible wavelenght, UV and other.The vast majority of the spectrum being in the visible light...

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...

I have 2 questions. 1)Can a gray body irradiate more than a black body for a given wavelength if both bodies are at the same temperature? 2)If the answer to the previous question is yes, do you know any material that irradiate enough in the visible spectrum that we can see it with our eyes...

Hello, If I understand correctly, the main contribution inside solids that result in the behavior of a black body at high temperatures is that the electron clouds vibrate around their nuclei. Please correct me if I'm wrong. If I'm correct: to get a black body spectrum every frequency...

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...

In wikipedia I've read that the Sun's surface temperature is about 5700K. The emission spectrum graph can be seen there: http://en.wikipedia.org/wiki/File:EffectiveTemperature_300dpi_e.png. I don't understand why the irradiance (or intensity I guess) of the Sun is greater than the one of a...

Homework Statement It emits protons with a frequency of 4 GHz, and has a photon energy of 2.65E-24 J. I tried to use the formula lambda=c/f=vT, but i am somehow getting a negative answer which doesn't make sense when trying to find temperature in (K). Any help is greatly appreciated.

Hi, I don't quite understand which are the fundamental processes for production of photons that are emitted by a "black body". Usually this is explained by considering a cavity in thermodynamic equilibrium but I am not interested in this. I am looking for a more practical description of this...

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...