Attenuation Definition and 119 Threads

It is known that the penetration depth of photon into a material depends on the energy of the photon, density and atomic number of the material; because the photon energy is normally smaller than the potential against the penetration of photon, which is the potential barrier, so the incident...

For my waves and diffraction course we have had a completely incompetent lecturer. We were looking at standing waves and then all of a sudden he spent a lecture looking at attenuation, not mentioning where it would apply or explaining it particularly well. I have tried to find a textbook to...

I was wondering why light transmission through a solution decreases exponentially and not linear with the concentration of the absorbing compound in solution. I know the Beer-Lambert law, but I do not really understand the reason for this logarithmic rather than linear dependence. Can anyone...

Homework Statement Is there any way we can measure the thickness of an exposed PTFE membrane air sampling filter? An unexposed filter (from the filter datasheet) has a thickness of 40μm. We have 5 ambient air exposed filters with the following mass concentrations: 1μg/m3 (filter 1), 20.1 μg/m3...

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...

I'm revising attenuation and power loss logarithmic equations. The exam formula I'm given is attenuation = 10 log (I1/I2) I'm trying to confirm what each I stands for. Some of the examples I'm looking at seen to give input/output power, some seem to reverse it. Which is right? What do they...

Homework Statement problem 1 A 20 Hz seismic wave traveling at 3 km/s propagates for 2000 m from point X to point Y through a medium with an attenuation rate of 0.5 dB/λ. What is the ratio between the amplitude of the wave measured at X and the amplitude of the wave measured at Y (i.e., AX/AY)...

I am completing a radiological physics experiment about attenuation and half value thickness. I'm struggling to understand linear attenuation coefficient and what it means when it says its and exponential relationship. I understand that attenuation is the reduction in intensity of an...

Why does water attenuate sound waves more than air? Is it because of it's bulk modulus? This is what I understand. Speed through a medium is determined by the elastic component over the inertial component. Since water has a much greater bulk modulus (elastic component) than air, it makes the...

This is killing me; not sure if I'm over-complicating or under-complicating it. I’m trying to understand if there is any difference between acoustic scattering and diffusion, and how that differs from attenuation. When particles collide, a small amount of heat is created, since the collision...

Homework Statement Find the attenuation constant alpha, phase constant β, and phase velocity v if the conductivity of the material is σ=ωε the material parameters are μr=1, εr =2.5, and the wavelength in free space is λ naught = 30cm Homework Equations The Attempt at a Solution So...

Homework Statement It is customary to express fibre loss in units of dB/km: \alpha(dB/km) = \frac{10log(P_{in}/P_{out})}{L(km)} where P_{in} is the power entering the fibre and P_{out} is the power leaving the fibre. Show that \alpha(dB/km) = 4343\alpha(m^{-1}) The Attempt at a Solution...

I have seen this concept in many places like electrical field, gravitational field, brightness from a distant star or in satellite communication. That is, they seem to be inversely proportional to the square of the distance from the source of that field. What's the reason behind it?

Hi, I have a question regarding frequency, power... Let's say I have signal with power level of X dBm and the signal has been attenuated by Y times. What is the correct formula to use to get the final power ? Thank You

Dear All, I am basically from Bio background and doing research in Insect Physiology as Phd. Currently I am given a task to generate artificial insect songs using a software. I did it with 3 v Noise stimuli(1.5 peak to peak) and fed it to amplifier and I heard it on Amplifier. So now the...

hello all first post here and I'm interested in some info you people may hold :smile: in layman's terms I'm trying to understand how a fixed line level can attenuate. according to wikis line level page the 'the signal out or line out remains at a constant level, regardless of the current...

Homework Statement http://img543.imageshack.us/img543/4598/photosfr.jpg Find dss, dsr and thus hs. Homework Equations trig The Attempt at a Solution dss = hs/(sin[θ]) dsr = hs/(sin[∅]) dss = 3.059/(cos[θ]) dsr = 47.191/(cos[∅]) θ = arctan(hs/3.059) ∅ = arctan(hs/47.191) I have tried...

I've been trying to get reantiquated with electormagnetics to understand RF communications better. I have a question about TEM plane waves. The funtions which describe the plane waves in the z dirrection are: e-α cos(ωt-βz) ; in the time domain where is the rate of decay. In free...

I have read that the attenuation of water (for ultrasound) is 0.0472 Np m–1 (MHz)–2. What is this in dB/cm/MHz^-2 ? What is Np? thanks

I recently did an experiment where I had a T-type attenuator. It was connected to a 50 ohm load, and as such I used a function generator with an internal impedance of 50 ohms. Doing the correct calculations, I found the source and load impedance were matched to the attenuator at 50 ohms...

Hello, I am reading this article in wikipedia http://en.wikipedia.org/wiki/Attenuation_length about attenuation lengths and there is something I'm hoping someone here can explain to me. Lets say I have one small solid sphere and one big hollow sphere. And let's say I put the small sphere...

I am trying to understand why radio waves are not greatly attenuated by the atmosphere due to scattering or absorption? I have tried searching the internet and can't find any satisfactory answers. Please help. Oh and does this property somehow relate to why they are used to transmit information...

Do electric fields attenuate in space? If so what causes the attenuation?

Hello. Not sure if this is the right board to post. This is not homework. I am just self-teaching quantum physics as I read a book on the topic of X-ray Physics. It has about 30 chapters in total and so far I find myself having about 3 questions per chapter. Hope you guys don't mind me asking...

Consider a wave propagating in a medium with complex epsilon (e). Show that the ratio of decay length to wavelength is roughly Re(e)/Im(e) when the decay length is long compared to the wavelength. --- I could attempt this if I knew where to start... not much help, but could anyone...

Hello, I'm having some issues with plane waves propagating through a medium which is: - linear - spatially and temporally homogeneous - spatially non-dispersive - isotropic - temporally dispersive - passive I know that permittivity, permeability and the k-vector are complex in...

Homework Statement I see graphs for the total mass attenuation coefficient such as this all over the web:http://scientificsentence.net/Radiations/images/attenuation_coefficients.jpg However, I can't find data on the individual attenuation coefficients such as the photoelectric or Compton...

I am researching how photon intensity attenuates within matter and am a bit confused by what I have come across. Several sources state that the attenuation of photon intensity within matter is exponential (as a function of depth). The explanation is that photon interactions with electrons in...

Hello, Why does electromagnetic wave intensity attenuate exponentially with depth from its incident intensity in an object? Why is the relationship exponential? I just need a nudge in the right direction or more if you are willing. Thank you for any help!

Why do we call the attenuation coefficient LINEAR? I(x)=Ioexp[-µx] why µ is called linear?

Homework Statement Show from general considerations that the attenuation of power in the rectangular waveguide (TE10 mode propagating in z-direction) is: P(z)=P(0)exp(-2k''z) where k'' is the imaginary part of the wavevector in the phasor exp(j(wt-kz)) Homework Equations power is...

Hi all, I can't figure this one out, but I'm sure I'm probably missing something simple. Here's the problem I'm having: From what I've been told in my SCUBA class (as well as from online article's and forums) light is attenuated in water in the order red->violet (red being attenuated first)...

Hi Forum, I am currently attempting to utilize http://bayes.wustl.edu/etj/articles/kramers-kronig.pdf" Unfortunately ... I have not been successful. I have tried for the past week and asked those around me. All help is appreciated. The equation is as follows: ( 1/c(w0) ) - ( 1/c(w) ) =...

Hi, I have been reading my textbook and online but I'm not sure if I understand. An EM wave attenuates in a conductor but not in a dielectric? If that is correct what does the impedance of a dielectric represent, since I thought impedance would be associated with an energy loss...

Hi, I'm having some trouble interpreting an equation. In Lamarsh's Introduction to Nuclear Engineering. The formulae for neutron attenuation is: I(x) = I_{0} exp(-\Sigma_{t} x I am given the formulae \frac{-dI}{I(x)} = \Sigma_{t} dx This formulae has been described as "the probability of a...

It strikes me that this may well be fairly easy, but i can't quite get my head round the correct way to lay this problem out (at least in a mathematical sense). If you are considering a neutron flux onto a fully understood material, and you also know the neutron interaction cross section of...

During my A level physics class we were discussing the attenuation coefficient of x-rays and a question arose that I can't find an answer to anywhere. If someone could help answer what effect physical state (ie gas/liquid/solid ect) has on the attenuation coefficient of x-rays it would be much...

is the linear attenuation coefficient named like it is because it is linearly proportional (inversely) to the energy? I have to read off the coefficient from a graph I have. I have the value for a 2MeV photon, if I want the value for a 1MeV photon is it simply twice the 2MeV value? Reading off...

Homework Statement near-field distance attenuation follows an inverse cube law (1/d^3), while in the far-field it follows inverse law (1/d). Prove mathematically how we arrive at 60dB/decade from the inverse distance cube relation and 20dB/decade from the inverse distance relation...

Hi all, using the mass attenuation coefficient and density, one can determine the percentage of X-rays absorbed in a material for a given depth, using the Beer-Lambert Law. e.g. The intensity of a beam of 8 keV X-rays will be reduced by 68% after passing through 70 microns of Silicon...

Dear folks, I'm a 3D computer graphics student, working on particles and fields area. As I'm a newer I have lots of doubts to clear on Physics topics. Please explain me what is Magnitude & Attenuation in Fields subject? I can see these two are common for most of the fields like air, drag...

Hi All, I'm reading about the attenuation of radio waves in space and I understand that, in addition to the normal attenuation that is proportional to the inverse of the square of the distance, there is also a loss due to the medium. This surprised me as I thought that there was no loss...

Hi, If we calculate the flux at a certain distance from a source of radiation by first neglecting the effect of attenuation in air, how does one factor in the effect of air attenuation? I do not know how to apply that theory. I'm am trying to understand what the difference is at sea level...

Hi, I am just curious; do EM waves attenuate in a vacuum? If yes, how does this happen? Also, how do they faint through a medium?

Dear All I am hoping for some insight into a transmission line problem I have been experiencing. I am quite inexperienced and unqualified in this area so if I am not clear please let me know. In wiring loom assemblies my employer offers there is a twisted transmission pair. The...

I would appreciate assistance with a thought experiment I've been having trouble with. What I asked myself was, If I had two Lasers of equal Intensity/power, say 200 milliwatts, one appearing green and the other red, with wavelenghts of say 555 nanometres and the other 660 nm, which laser...

Does anyone know how to filter 60 hz down to -140 db all the notch filters I tried are about -60 db maximum but after I amplify the signal to 100db the 60 hz becomes a problem again. I need a filter for this it doesn't have to be one stage and also I need the 100hz, maximum attenuation on 100...

I need to know the practical applications of the absorption of gamma rays in materials.

Homework Statement I'm writing a school paper on the behavior of electromagnetic waves when they hit the interface between a non-conductor and a conductor. My question is if, in the case of partial reflection, it is correct to allow for both components of the wave vector (the wave is...

Hello, I'm attempting to analyse the data recovered from an experiment that I performed in lab, but I'm having some problems understanding how to properly apply the statistical methods learned to this specific problem. Essentially, the experiment consisted of placing a source of gamma rays...