Radiation Definition and 1000 Threads

Homework Statement A spherical body of area A and emissivity 0.6 is kept inside a perfectly black body. Total heat radiated by the body at temperature T is (A) 0.4σAT4 (B) 0.8σAT4 (C) 0.6σAT4 (D) 1.0σAT4 Homework Equations Stefan-Boltzmann's Law: P = AεσT4The Attempt at a Solution If it wasn't...

Hi! I hope this is the right place for this question. I have a plot of mJy vs frequency and I want to fit a blackbody plot to it. I just don't know how to convert the y-axis correctly to use the formula for the fit. Any help is appreciated.

Hello, I'm looking for a gas (hopefully one that is readily available) that will absorb Nd:YAG laser radiation at 1064 nm. The purpose is to heat the gas to transmit heat into a glass fiber composite which normally does not absorb IR light.

Hello All, I just got my B.S. in Physics and am now beginning a PhD program in Nuclear Engineering focusing on radiation detection using semiconductors. I very much enjoyed my Physics degree and want to stay in fundamental research for my career, in which case I would also say, I have no...

Can ionising radiation (gamma rays) diffuse incandescent light bulb filled with inert gas ?

Homework Statement In a dark room with ambient temperature T0, a black body is kept at a temperature T. Keeping the temperature of the black body constant (at T), sunrays are allowed to fall on the black body through a hole in the roof of the dark room. Assuming that there is no change in the...

What kind of radiation that can penetrate basically everything including thickest lead and concrete? Even the strongest radiation, so far, such as radio wave and gamma ray can be stop by thick lead and concrete. So, is it possible that there are kind of radiation that pass thru everything?

Hello, Are there any Plank Radiation Spectrums for liquids? What I really want to know is, for a given liquid, what wavelength of light is emitted for a given temperature. For example, if I journey to the center of the Earth, the molten lava is about a thousand degrees, hot enough to emit red...

Hi, I recently read that as temperature increases, atoms move faster and have higher frequencies, shorter wavelengths and more intense radiation. What does intense mean? Does it mean in a substance there are a greater percentage of atoms emitting at higher frequencies or does it mean another...

Microwave oven operates at 2.4 GHz. Consider the situation of making tea or coffee in Microwave where water is heated to 100C to boil. Looking at Planck's law / Wien's law, 100C (373K) corresponds to a peak wavelength of 7.8nm or 38.6THz which is in Mid Infrared. Effectively materials...

Today on NPR "On Point" the program was discussing the Scott Kelly mission. One of the experts said one important thing to investigate is what radiation he received and how it will effect his body. My question is, isn't that fairly easy to measure? What kinds of radiation mitigation could there...

Hello! Could you teach me how to measure the radiation intensity(exp infrared) from fireplace? Can i observe radiometer to know about intensity of fireplace flame?

Hello, I read a lot at this forum about thermal radiation but still i have questions. Consider black body at some temperature T. It means that inside that body we activate many modes of quantum oscillators with some probability(Bose-Einstein) depend on temperature T. Now let's have some bulk...

If someone was splashed with 5 ml of reactor pool water over 10 cm^2 of there skin, how much dose they will receive? note: the tritium was created in the reactor pool water. Also if they swallowed 125 ml of pool water how much dose they will receive ? Thanks.

1. If I throw sixty different dice (compared to an atomic nucleus) and each dice that gets a 3 is disintegrated and disappear before the next roll. Altogether I make ten roll, where each roll corresponds to one day. The result is illustrated in a graph: http://imgur.com/TbXF4mf click on the...

Is there a limit as to how much a black hole gathers mass and how much it losses mass via hawking radiation so that the black hole becomes in equilibrium, neither gaining mass or loosing mass How long would it take a hypothetical isolated black hole to loose one solar mass due to Hawking radiation.

This question is about transmission line that I use between my Ham radio and the antenna. We a transmission line that is made of two parallel conductors close together. The current in one conductor is exactly the same as the current in the other conductor, but flowing in opposite direction...

Hi, Very basic question. Blackbodies are ideal emitters: at every frequency, they emit an amount of energy equal to or greater than any other object at the same temperature. Furthermore, they were named blackbodies since, AT ROOM TEMPERATURE, i.e. 300K, whatever radiation they re-emit (after...

When 2 black holes coalesce when is the peak energy created, when the BHs are close together or when they are fully merged.

Hi. Dunno if this makes much sense. If radiation is emitted from a star with a certain frequency, does that frequency change, if that radiation travels through areas of different temperatures?

I see that black body radiation slowly depletes a body's thermal energy, which is just another way of saying that black body radiation depletes the kinetic energy of a body's constituent particles. But does black body radiation also cut into the kinetic energy of the body as a whole, such that a...

Hi everyone, The charged particles in the magnetic field around the neuton star, is accelerated along the magnetic field lines, which would go in a curve, from the north pole to the south pole. Due to the acceleration the particles will emit radiation, along their movement axis, and because the...

Homework Statement A solenoid contains 610 cycles, with a radius of 0.136m and a length of 0.87m. The current of the solenoid decreases linearly from the maximum value I0 to zero through the equation I(t)=I0−bt, where I0=0.31 A and b=0.21 A/s. What is the power output of the electromagnetic...

Hello everyone. Is there a type of radiation detector that can tell the energy level? I have a basic understanding about Geiger counter and Scintillation counter, they seem only tell the incident particle number. The testing environment may contain Thorium series, Uranium series and Actinium...

Where does the emf radiation from an elliptical come from? Just the console? I just read an article about dirty "electric pollution," and I was wondering.

-iation. Could the opacity of a material to one band of EM radiation (light) could be altered by irradiating the material with another band of EM radiation (X rays)? I think you are suggesting that: By raising the electrons in the atoms to higher energy bands (with the X rays), so that they will...

Suppose a shield that is infinite in the y and z directions and of thickness 1 meter in the x direction is constructed of alternating layers of materials A and B. Will this shield attenuate a beam of neutrons with more or less or the same attenuation that it would if it were constructed of the...

Does electromagnetic radiation emitted by cold hydrogen gas travel at the speed of light?

Homework Statement At what rate does a 0.1m cube of metal with emissivity e=0.75 radiate energy if it is at a temperature of 200C? Homework Equations H=AeσT^4, σ=5.67 x10^-8 The Attempt at a Solution I found the area of the cute to be A=(0.1m)^2=0.01m, and the turned 200C into 473K, but when...

Homework Statement Compute the radiation pressure exerted by a gas of photons (according to kinetic theory). There are N photons, each with energy hf, the momentum is hf/c, and the walls are perfectly reflecting. Express the pressure in terms of N, V, and the product hf. Homework Equations...

https://www.sciencenews.org/blog/science-ticker/first-run-gravitational-wave-search-winds-down-rumors-abound?tgt=nr May be i was wrong and there is GR's, but this article is speculative.

Homework Statement t has been proposed that a spaceship might be propelled in the solar system by radiation pressure, using a large sail made of foil. Assume that the mass of the ship + sail is 1780.4 kg, that the sail is perfectly reflecting, and that the sail is oriented perpendicular to the...

How come that, in the context of discussing the search for gravitational waves, I never see the cosmological constant mentioned ? We know that ##\Lambda \neq 0##, so this seems strange to me; in the presence of a non-vanishing constant, the background is not Ricci flat in the vacuum case, so...

Is there anybody on the forum who is up to speed with the ins and outs of these devices? 99% of research papers and all manufacturers comment I have read say these devices are working because the distant object emits radiation that the detector absorbs and therefore this absorbed energy *heats*...

Homework Statement 2. Homework Equations [/B] Given in the question. The Attempt at a Solution [/B] For part a I obtained an expression for the the dipole moment: ##P(t)= P_0 cos(wt)## And therefore, for part b, I obtained the expressions ##\frac{dP}{dt} = -wP_0 sin(wt)## and...

Freon is used every day to reduce temperature by compressing the gas then releasing the pressure. The Question is dose radiation from the sun (witch would be high pressure) steal energy from the objects it comes in contact with in space (witch is low pressure), Thus contribute to the loss of...

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...

A typical example is a iron chair gets cold in winters and wooden chain not. We all know iron is more conductive but how this thing possible at molecular level of conduction of heat from metal to air. In general conduction I know it is possible due to vibration transfer of molecules but how it's...

First, I hope this is the correct place for this question. I am experimenting with electrical discharges at low pressure, think plasma globe, and I bought a geiger counter to make sure I am not producing x-rays. My vacuum pump is rated down to 5 pascals. The problem is that the geiger counter...

I am confused with the fact of radiation pressure on Wiki and my homework solution. They are both arguing that the pressure produced by a ray of light to be reflected with incident angle θ and intensity I is: $$\frac{2I\cos^2(\theta)}{c}$$ My thinking We know that: $$Ft=\Delta p$$ We see the...

hi, i'm student in a university. I do not understand the definition of these concepts, and I would like to know the properties of these and it depends questions like They depend on the material used? the atomic number? thanks for answering capisko,

Hi guys/girls, Been out of school for 2 years due to some circumstances but now I've got motivation and determination to get into the mentionned program. I'm insanely nervous about the letter of motivation and interview in the admission's requirements. I don't know anyone who could proof read...

I'm trying to understand the meaning of kT (energy) in molecular systems, how to define the temperature of an individual molecule, and how a molecule receives thermal energy or dissipates thermal energy. Here is my 'gendanken': One molecule is floating in a box, in vacuum. The temperature of...

Im trying to compare, visually in my head, the difference between transmitting data vs something like radio or microwaves vs how inductance and capacitance. I understand that the way the wave is modulated for example, AM or FM, can be interpreted as 0s or 1s. Im trying to compare this to...

Hello everyone, I have heard in a sminar that radiation is the highest form of entropy. Why? I was wondering too if all matter would transform at the end in radiation somehow

Why is it that the smaller the black hole is, the more quickly it supposedly evaporates? It seems like a black hole should radiate energy proportional to the surface area of the event horizon. To me it seems like the evaporation should slow down the more the black hole shrinks because the energy...

Radiation dominated the universe 4,700yrs to 378,000yrs, do the facts in the literature mean there was no baryonic matter between those yrs or was there still plasma or some sort of mass?

Since Schwarzschild solution describes exterior not only of black holes, but of any spherically symmetric non-rotating objects, then any such object should emit Hawking radiation, no? Then how exactly is that working? Let's set up a thought experiment. Say, we construct a spherically symmetric...

I just had a flashback to an applied electromagnetic course I took a few years ago. I believe we were learning possibly about waveguides (maybe) or something, but there appeared a phenomenon in the math that made it appear as if the wave was traveling faster than C. When asked about it, the...

I am following Vaidya metric and how it is related to pure radiation from Wikipedia. But when it reaches the line where stress-energy tensor is equated to product of two four-vectors, I cannot follow from where they are assumed to be null vectors, and why if the stress-energy tensor is given in...