Radiation Definition and 1000 Threads

Homework Statement I am doing an assignment with multiple heat transfers, and have to investigate the effects of including thermal radiation vs saying that thermal radiation is negligible. I know that the equation for thermal radiation is q = A*σ*(T14 - T24) (*) In my case the equation...

have read numerous times about Hawking radiation. don't understand how that can lead to black hole evaporation in so much that wouldn't as many matter as anti-matter particles fall in thus balancing out over time to the growth and evaporation of black holes thus leaving the mass of the balck...

Hello. I want to calculate how long time it takes to heat an object with radiation. The object is the inner cylinder of two concentric cylinders. The inner cylinder is not hollow. If assuming black body: \dot{Q}_E=\sigma A_1(T_1^4-T(t)^4) [1] Energy emitted must the same as the energy...

My understanding of electromagnetic radiation is this: When a charged particle accelerates, there is a change in its associated electric field at all points in space, though not instantaneously. The "electric field wave" is basically the propagation of the disturbance that occurs when the...

The classical problem of radiation reaction classical electrodynamics seems to be a huge mess with no good answer. There is no even consensus of the very form of the Newton law "predicted" theory. So, the question of this thread is: Does the classical limit of QED say something about this...

Hello. I'm using coaxial cable to transfer power to the load with original aim that radiation from the coax would be low or almost nothing as current on both conductor (central conductor and outer shield layer - ground) are equal in amplitude and opposite in phase so their sum is zero; zero...

A blackbody is a theoretical object that perfectly absorbs all the light that falls on it. From what I understand this is an ideal situation and does not actually exist in reality. Certain objects are close to being a blackbody but they do not absorb 100% of the light that hits it (i.e. some...

Hey all, is there a formula that can calculate the energy losy by a photon traveling through air at 1 atm per meter given frequency? Any help apreciated.

Homework Statement U = u(T)V; P=u(T)/3 a. Find (ds/dt)v and (ds/dv)T in terms of u. Ans. (ds/dt)v = 1/T[du/dt] and (ds/dv)T = 1/T[du/dv + P]...Correct b. Show that u(T) = Const*T^4 equate partials above and integrate...Correct c. Find a Relation between V and T during adiabatic compression or...

I think the equation for the relationship of the E (electrical) and B (magnetic) fields in electromagnetic (EM) radiation is E=Bc, where c is the speed of light. I think this is correct, but what does it tell us? On it's face, it looks as though the B field (of a photon, say) is...

Hello, I will try and provide as much detail to the problem as I can with the hope someone can help me solve this. We are currently working on a wireless project that contains high electrical currents, because of this the box the electronics are enclosed in experience quite a temperature rise...

1. Homework Statement A piece of work I am doing for college (UK college that is) has me investigating the inverse square law for gamma radiation. I have collected data and the graph comes out looking right. I want to create a linearised graph of the data to investigate the results further. If...

as described by einstein in his paper published a few days ago in 1917, photon emission can be spontaneous or stimulated. In stimulated emission, atoms can be in an 'excited' state and the passage of a photon through such a population can can cause the ejaculation of energy in the form of an...

If radiation from the big bang has been traveling away from it's origin, how can it arrive at the same point from opposing directions?

Hi, Its been a while since I had my thermal heat transfer classes and I am a little skeptical on what I remember. Im trying to insulate a copper block, the sides are covered by an insulating material which has a low thermal conductivity (they are touching). Howver there is a surface on the top...

Light consists of photon Photon is carrier of energy When lights are switched off where had the energy of photon gone According to law of conservation of energy Energy can't be destroyed In darkness, are they any radiation due to conversion of energy??

Homework Statement There is a radioactive source plaed in front of the GM counter to predict the kind of radiation emmitted by the source. 1 : When the GM counter moves 5 cm away from the source, the count rate drops significantly. 2 : When a 5mm aluminium sheet is inserted...

I'm trying to start understanding quantum mechanics, and the first thing I've come across that needs to be understood are black bodies. But I've hit a roadblock at the very first paragraphs. :( According toWikipedia: A black body (also, blackbody) is an idealized physical body that absorbs all...

http://www.cengage.com/resource_uploads/static_resources/0534493394/4891/Ch03-WebAppendix01.pdf I've been doing some reading and I came across a mathematical step that is confusing me. Could someone explain to me how they get from equation 3.45 to equation 3.46 in the link that I have posted...

Hello everyone, Can atomic or subatomic neutral composite particles that consist charged particles emit cherenkov radiation if they are polarised strongly enough (and are fast enough)?

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...

Here, I read about non-thermal radiation sources: http://astronomy.swin.edu.au/cosmos/N/Non-thermal+Radiation 1- when an accerelated charged particle emits EM radiation, so it must lose energy. What does happen finally to electrons radiating in synchrotron process and what is the frequency of...

Which radiation emitted by an electron that moves in a circular motion ? And how radiation can be emitted by an elementary particle?

I got this off ebay for $55. This is one that was used at the Peach Bottom Nuclear Generating Station in Pennsylvania. It measures in mR and has both a rate and dose alarm that can be set for a custom amount. Uses one 9v battery. Not really sure what I can use it for, but I was thinking about...

I read that Cerenkov radiation is caused by charged particles traveling faster than the speed of light in the medium, but I don't understand why. I have seen analogies to a plane moving a supersonic speed creating a cone of sound waves because the waves can't keep up with the plane, but in this...

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...

Homework Statement Show that the total energy of the radiation in a volume V at temperature T is Hint: Homework Equations The Attempt at a Solution The hint doesn't make sense to me, and those are the equation that I found to be perhaps relevant. Do I integrate the second equation? I'm...

I have seen the radiometer (mill in a bulb with differently coloured leaves) explained by thermodynamics, but also this: where little particles are propelled by laser beam. So, does light beam actually transfer or cause momentum in some way? If it does, is there any chance to make a...

Why do people worry so much about microwave radiation if it has less energy than infrared (heat) radiation? Why do they worry about STANDING near microwaves versus standing near heat sources? Why do they worry about using it to heat up their food if it's lower in energy than infrared?

Hi dears,i have a question about atom,in classic physics ,(Bohr theory) when a electron swing away a proton it have not radiates magnetic waves because if electron radiates magnetic wave it will drop on proton ,and atom will be Unstable! my question is ,in quantum mechanics that uses orbitals...

Will particles that don't interact with normal matter (dark matter for example) emit cherenkov radiation (if light in that medium moves slower than that particle) ?

Homework Statement Consider a snow-covered surface. Assume that the amount of solar radiation that reaches the top of the atmosphere is 1367 Wm-2. Given that 50% of this solar radiation is either absorbed in the atmosphere or reflected by clouds before reaching the the snow covered surface...

Homework Statement How much heat is radiated in water per sq cm, from a block of copper at 250 C and 1200 . Homework Equations e= 0.6 Hr= (Area)(e)(5.67x10^-8 W/m^2K^4)(temperature)^4 The Attempt at a Solution i'm sorry, i don't know how to solve this one...

Hello everyone! I had a question about a particle (say a proton) with relativistic energies interacts with a magnetic field (in the z direction). As it is accelerates the particle emits synchrotron radiation. Naturally I assume that this emission of photons reduces the particle's energy. My...

Hi there, I´m reading about the theory of radiation and came up with some doubts when I started to calculate the net flux that an observer would "see" coming off from the star. I have provided my answers to my own questions but would like to see what you people think about them. 1. Can it be...

How can I compute the intensity of an electromagnetic radiation if I know ##e_x, e_y, e_z, h_x, h_y,## and ##h_z##, where ##e_i## is the electric field component at ##i## and ##h_i## is the magnetic field component, also at ##i##? Thank you in advance.

Homework Statement Consider a small, spherical particle of radius r located in space a distance R = 3.75 × 1011-m from the Sun. Assume the particle has a perfectly absorbing surface and a mass density of ρ = 3.8-g/cm3. Use S = 214 W/m2 as the value of the solar intensity at the location of the...

Homework Statement A space probe carry an instrument that detects radiation in space, the area of the probe is ##5000 \, cm^2## and its collecting data for 10 minutes. The information sent back to Earth is given from this image below, how much radiation energy is it for 10 minutes...

In the energy balance of a system where a small object at T1 enclosed in a body at T2 given by the Stefan-Boltzmann equation q = A1ε1σT14 - A1α12σT24 shouldn't it be a differential equation since the small body could be absorbing/releasing sufficient net energy from the enclosing body that...

Homework Statement We have a sensor onboard a satellite that is faced towards Earth, from the Sun. The LW absorptivity is 0.8 (a_LW) and SW is 0.2 (a_SW). I need to find a equation for the temperature as a function of time. Given datas is the Area=0.3 m^2 and Specific Heat of 4 J/K Homework...

bapowell submitted a new PF Insights post A Poor Man's CMB Primer. Part 2: The Birth of a Cosmic Background Radiation Continue reading the Original PF Insights Post.

Hello, new to the forum. I am currently in high school taking a full load of college classes through dual enrollment. I will graduate high school with an Associates of Science degree. I really enjoy math. It has always been my favorite subject. At the moment I am in Calculus 1 and it isn't so...

I'm not sure where to ask this question or if it even makes sense... Say an electromagnetic wave passes through a point in space. The point experiences some fluctuation of electric and magnetic fields. But what happens after the wave has passed? Are there any lingering effects, like a "wake"...

Consider a dipole antenna that is radiating at it's resonant frequency F. Consider an observer approaching this dipole antenna, in a direction perpendicular to the axis of the dipole, at velocity 0.6c. According to the relativistic doppler shift, the frequency perceived by the moving observer...

Q. Regards infrared radiation, conduction and convection, is infrared radiation the starting point, the fundamental source of heat energy (thermal energy), and the fundamental source of the other two? I’m thinking that the Sun predates the Earth by 30 million or so years so the first heat...

If only 14% of the total solar emission is in the UV region, why is ozone depletion a cause for concern. Considering that only a small fraction of the sun's total radiation reaches earth.

Consider the heat equation dT/dt - aΔT + v⋅∇T = S where S is a source term dependent of the radiation intensity I and the temperature T. The fluid velocity v is prescribed. We also consider the radiative transfer equation describing the radiative intensity I(x,ω,t) where ω is the ray direction...

I have no idea how lethal/strong space radiation is, but i do have an idea that most of it is from the sun perhaps? I also know that the prime factor to deflect this radiation is magnetic field and the ozone layer. I think the magnetic field handles only particle radiation and atmosphere handles...

How is a continuous chain reaction maintained within a moderator if it is not fissile material? Are the fissile materials mixed with the moderator or are they coalesced at the center of the surrounding moderator? If it is the latter, how would the surrounding moderator allow fissile material to...

The book is expensive, so I want a book like Bekefi's and Barrett's Electromagnetic Vibrations,Waves,Radiation. Preferably at a higher level than this book. Thank you!