Radiation Definition and 1000 Threads

Consider this: Two antennas are set up in a vacuum. They both radiate electromagnetic waves of the exact same frequency, and an interference pattern can be observed on a screen placed some distance away. Now suppose the emission density was reduced (in both antennas) to one photon at a...

Can you guys give me example for conduction, convection, radiation energies ?

Homework Statement A cavity contains black body radiation at temperature at T=500K. Consider a optical mode in the cavity with frequency w=2.5x10^(13) Hz. Calculate; (a)the probability of finding 0 photons in the mode. (b)the probability of finding 1 photon in the mode (c)the mean number of...

Homework Statement To protect the lunar base against space and sun radiation, astronauts covered it with 4m thick layer of regolith (moon soil). However, they found that they level of radiation was still 50% higher than on the Earth's surface, which they want to match. How many more meters of...

Where does thermal radiation come from? vibration of the molecules or the excitement of electrons ?

Hi, I am reading about how a radio station may "null fill" to direct RF radiation downward from the broadcast antenna; without this the area where the antenna is located would not receive a good signal, if any. Does anyone know what limits apply to this? If someone...

Does the existence of observer dependent particles as predicted by the Unruh effect and Hawking radiation lead to paradoxes?

Why aren't the other bands (visible, UV, etc.) in the electromagnetic spectrum also seen today as part of the background radiation?

Okay, I will be the one in the class that asks the questions that some of us are afraid to ask but still want to know. How could the light from recombination, which occurred about 380K years after the Big Bang, interact with the gravitational waves generated from inflation, which occurred...

This article mentions moon dust as "subjected to a millenia of UV radiation" as if it's a bad thing. UV would simply irradiate the dust, not make it more hazardous correct? Perhaps they meant "a millenia of cosmic radiation" which would be much more problematic, no? If this line of...

I have a solid foundational understanding of far field electromagnetic radiation i.e., two in phase electric and magnetic fields oscilating perpendicular to each other and to the direction of wave propagation. However, I have some ambiguities regarding near field electromagnetic radiation and...

Hello everyone, I'm a radiation therapy 4th year undergrad student about to pursue some research in medical physics as a 4th year thesis project at a hospital. However I am really not sure what my thesis project should focus on. Because it is mandatory to conduct research on your original idea...

Can you make an educated guess on the amount of energy in the universe in the form of electromagnetic radiation (photons), considering the vast amount of photons moving in every direction throughout the vast universe, there is literally no point in the universe that you can be in and not observe...

say you measured every particle which has entered a black hole say you measured every hawking radiation particle which exits the black hole my understanding is that if like... a proton enters the black hole, then an anti-proton needs to be emitted via hawking radiation. so if you measure...

does thermal radiation involve ultraviolet x ray and jamma ray or just heat of light...

I was wondering what experiments or observations have shown that the cosmic microwave background radiation exists outside our galaxy in intergalactic space. Have we detected it emanating from sources outside the galaxy? I know we've detected it here on Earth.

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...

It seems there was an unexpected radiation release within the WIPP late last Friday, Feb 14, 2014. While there are no reported injuries or external radiation leaks reported, there have been no follow up reports from the DoE apart from the very sketchy initial confirmation of the incident...

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...

Ionization radiation vs "ordinary ionization/electrical breakdown" Hi, I hope I get understood correctly, my question is seemingly simple: Why is ionization radiation( energetic rays like gamma rays) dangerous and vastly different than say any common everyday ionization from a normal...

From what I understand, Hawking radiation results when one virtual particle (of the pair) falls into the black hole while the other escapes... See I understand why the virtual particles don't come back together - because one is created beyond the horizon while the other is not. But how...

I was doing my casual tuesday experiments class. Me and my 2 "coworkers" were given the task of creating a function that gives radiation as a function of distance. I was given a sample in a black box, the rest of my team was on the sensors. I took it out and it said "Do not handle unless out of...

Hello! I've been working on this physics problem for a physics II course and I'm stumped. Maybe someone can assist? Homework Statement A small insulated copper sphere of radius 0.001m is illuminated with radiation with wavelength 300nm. What is the maximum charge accumulation on this...

Homework Statement The minimum wavelength observed in x-ray radiation is 1.23 angstroms. (1 angstrom = 10E-10m). What is the KE, in eV, of the primary electron hitting the target? Homework Equations eV = hc/λ and since all the potential energy becomes kinetic... is the answer simply...

http://www.bbc.co.uk/news/uk-england-cumbria-25975785 They have/had "above normal levels" at a perimeter detector. As far as I know this would detect airborne radiation. And presumably at far lower levels than the source. "A spokesman stressed there was no risk to the public or...

Hello! I'm not really into physics that much, and in school I didn't study it that much either, so this question will probaby look silly to you. I have a question about radioactivity: When an object/human being is exposed to radiation, does it continue to emit rays? Because in most...

I'm trying to figure out which layers of the sun emit different types of radiation For instance; I know that most of the visible light is emitted from the photosphere but what about IR, UV, x-ray, etc...? Anyone know?

This post specifically queries the absorption, by matter, of (thermal) radiation which has been emitted from a source of a cooler temperature than the receiving matter. As I understand it, when matter 'receives' radiation, that radiation is either a) absorbed, b) reflected (or absorbed and...

Can someone help me on this: Hawking Bernstein radiation can cause a BH to evaporate. The second law of BH dynamics says that the area of the event horizon cannot decrease. Isn't this a contradiction? Also when considering the size of the event horizon, is it different depending on wheather...

Hello, I have a question: Do stars have Van Allen Radiation? Thanks

Homework Statement \mbox{Let} \ p(< \nu_{0}) \mbox{be the total energy density of blackbody radiation in all frequencies less than} \ \nu_{0}, \mbox{where} \ h \nu_{0} << kT. \mbox{Derive an expression for} \ p (< \nu_{0})Homework Equations p(v) dv = \dfrac{8 \pi h} {c^3} \dfrac...

Hi all I understand that at high frequencies, a twin lead Tx line has high radiation losses because the conductor separation becomes close to the wavelength size, allowing the conductors to act as antennas. Can one still be used to transfer a high frequency signal a short distance from an...

Hello, I was wondering how I could go about finding the wavelength of light that would cleave the O-H bonds of a water molecule. I looked up the bond dissociation energy of the O-H bond, and it is 460 kJ/mole. Now, since there are two O-H bonds, it should be twice as much, 920 kJ/mole...

Since we can observe gravitational lensing and conclude that mass can affect the path of EM radiation it seems logical to me to assume that EM radiation will exert a slight gravitational attraction of it's own on a mass,- although I do not recall ever reading about this. Presumably the...

Hey, as per i know pulsars emit EM radiation . . . Can anyone please explain the reason behind this in terms of quantum mechanics. I want to know what happens at the quantum level. All I know is that it takes place due to misalignment of magnetic and rotational axis... I am in high school...

Hi, please could someone help as I have got myself desperately confused with how radiation interacts with matter largely because of conflicting sources on the internet. Apparently there are 2 main types of interaction of radiation with matter; atomic/molecular vibrations and electron...

So as I understand it Stephen Hawking and one other person I can't remember the name of worked on an equation to described the "temperature" of a black hole, that you can actually get information out of it. I know that there is one way it could happen with those vacuum particles in vacuum energy...

Hi, If I were given a whole-body X-ray dose daily for many days (a year for example) What would be the highest dosage per day which would result in an increased cancer risk but no noticeable signs of radiation poisoning by the end of the year, or during? And also, I've read that a 2KRad dose...

I was just wondering if ionizing radiation can split water into hydrogen and oxygen? Thanks in advance :)

$${\rho}({\lambda}) d{\lambda}=E({\lambda})*f({E(\lambda}))*D({\lambda})d{\lambda}$$ $${\rho}({\lambda}) d{\lambda}$$ 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...

Homework Statement What is the meaning of the peaks (for example between 100Kev and 400Kev) in a energy distribution of transmitted electrons graph where the y-axis is probability density (1/eV) and the x-axis is energy (eV) ? When we simulate a source of photons with a given energy...

Homework Statement Consider the electromagnetic radiation inside a kiln, with a volume of 1 m3 and a temperature of 1500 K. Calculate the radiation pressure inside the kiln. How does it compare with the air pressure? Homework Equations PV = NkT The Attempt at a Solution I got...

Hi, I an reading an interesting chapter of Feyman where he explains the basis of light-matter interaction with wave theory: http://cua.mit.edu/8.421_S08/Reading/Feyman_refr_index.pdf I didn't understand there one thing... to explain it he says that all the dipoles on the plate ''feel''...

Hi, I have to plan and carry out an experiment on thermal radiation as part of my physics lab module. The description of the experiment is as follows: Investigate the radiation from a bulb filament as a function of input power, using a pyrometer to measure the temperature of the filament...

Hello, first of all, I must say that I am quite knowledge lacking in the thermodynamics topic, I am just seeking some intuitions. From what I have read so far, heat can only flow from hot bodies to cold bodies, and not the way around, according to the 2nd law of thermodynamics. According...

Homework Statement A powerful research laser produces pulses of light, wavelength 527nm, containing 300j of energy in 1.0x10^-9 seconds. and concentrated into an area with diameter 1.0x10^-4 m. Assume that the pulse is uniform over its area and uniform in time over its nanosecond...

Why do we often treat the electromagnetic radiation effects on Hamiltonian of a matter as a perturbation? In the other words, why the effects of radiation is so little that is treated as a perturbation?

When an electromagnetic wave is impinged on a semiconductor and we solve the perturbed Hamiltonian by taking into account the vector potential in the momentum term, two terms would add to the unperturbed Hamiltonian which one of them deals with absorption while the other with emission. I like to...

Hello, I am a business student currently collaborating on a technology project whose aim is to find alternative applications for a radiation detector made from artificial diamond. The main benefits of the detector are: • Ultra-fast response time • High durability in really harsh...

This isn't really a homework question, but I felt it was better suited here than in General Physics. I'm looking for more of a general explanation than anything. I was able to do my homework for this section on my own (mostly), but I feel like I still really have no idea what is actually going...