Propagation Definition and 457 Threads

Does anyone know the Lagrangian for the propagation of light in curved spacetime? I'm disappointed to discover that I don't actually know how to compute the action for a given null curve.

I am modelling a radio wave propagation simulator for a Wifi at 2.4 Ghz. I know that the refracted index of glass for light is around 1.5, how do I translate this to a 2.4 Ghz radio wave. And what about other materials, such as concrete, brick wall etc. Thanks.

Could you possibly comment the following statement: 'Heat propagation is a semi-deterministic process in that its future is determined by its present but not by its past.' Is heat propagation a violation of the determinacy and reversibility of the laws of classical mechanics? Thanks

Hello, there is a subject of wave propagation and collapse that has plagued me for some time, and although i must have heard about it, my memories are probably skewed ( i studied EE and had high frequency, physics of materials and nuclear/quantum physics sometime in 1970s :) as subjects). In...

I know 75ohm CATV coax is anything but ideal for 2.4GHz, but I am still curious as to how far these signals will travel upstream through the existing local cable network (splitters, etc) laid by the cable company, and if they could be transmitted between adjacent houses on a street. Example: an...

Hello If I entangle to atoms in close proximity to each other, is there any way I can separate these atoms by a large distance and maintain their entanglement? Thank you.

In the same sense that sound waves propagate through air, water waves through water, light through spacetime, what medium does the de broglie wave propagate through? Also, how could one detect such a disturbance in this medium without measuring the particle itself? (i.e. you can see the wake of...

Homework Statement This is about experimental physics. I have a value of resistance R=9000 \pm 1000. Then I had to do the following calculation: \frac{40000}{9000}=4.44 \ \Omega So, I'm not quite sure how to calculate the final uncertainty from my uncertainty \sigma = \pm 1 \ k\Omega...

I'm having trouble understanding why only certain angles of propagation can transmit down an optical fibre. My lecturer produces this formula for the allowed angles: \sin \theta = p \frac{\lambda}{2dn} where \theta is the angle of the ray from the optical axis \lambda the wavelength of light d...

I recall that when in school, teacher said that during a wave propagation, be it the longitudinal wave (like sound wave) or transverse wave (like water surface wave), particle in every position only oscillate along its equilibrium position, and will not experience translational motion. i.e., if...

Hi everyone, I have a specific question regarding the nature of electromagnetic waves. I understand he basics of EM waves (frequency, amplitude, wavelength, etc.) and that 'it' is a pair of oscillating fields; one electric and one magnetic, perpendicular to the direction of travel. What I...

Hi Guys, I came across this article by Jikang Chen and it is of importance to me to know what measure of credibility this concept holds in the general physics fraternity. I do not have the background to make sense of the mathemetics or physics cited. I would appreciate your comments. The...

Okay, so I have an assignment for uni and my friends and I need to work out some info to fill out an excel document, however we're not sure exactly what it is that we're looking for. The section we're stuck on, as the title suggests, is the 'error propagation' section. Are we looking for the...

my question concerns electromagnetic (EM) wave propagation. consider a two layer medium where the first layer has constant conductivity $\sigma_0$ and the second layer constant conductivity $\sigma_1$. If a EM wave propagates from the first medium into the second one boundary conditions have...

The intensity (W/m^2) of an electromagnetic wave from an ordinary antenna decreases with the square of the distance from the emitter (in the far field.) Is the same true for a laser beam?

So if a single photon is emitted and it travels as a wave, then it should lose its energy by distance squared. But how can it possibly do it? -its a single photon, so its intensity cannot really change, can it? What - you will have a half of photon? What does that even mean? How can it be like...

huy there! everyone says that light has wave particle duality. it means light is a wave and also consists of a particle. now, wave is a disturbance in a medium. but, we know that light can travel without a medium. then why do we say it is a wave? (i know that it is a non mechanical wave then why...

I've read in various places on the web and on this board discussions regarding subwavelengths, but I still can't fully comprehend how it's possible for an EM wave to transmit through an aperture and\or encased waveguide that is smaller than the given EM wave's wavelength. I've read about...

Dear Friends, I am new to this forum and I am not sure whether I am writing my Query in the correct section or not...If not Kindly guide me where to post this... I am confused about what are normal modes of propagation in isotropic or anisotropic media?? or How one can define Normal modes...

I am trying to figure out how the TEM wave looks like and how it propagate outward. Attached is a pdf of a drawing with only the solenoid and show the winding that the current is flowing in CCW and a reference. Also I draw a loop with one resistor and show the induced current and the polarity of...

Please confirm the direction of propagation for me. If the E field is defined as: \vec E \;=\; \frac{\mu_0 k}{2}(ct-|x|)\hat z 1) With this equation, the direction of propagation of the E field in both + and – x direction even though the \vec E = \hat z E_z? 2) The E field is not...

Hi All, In wave theory, we learn that Huygens' principle apply and that every point in a wave front acts like it was a source. According to this, it seems that from a given wave front we would see, after some small time interval, not only the the propagated wave front but another one...

Homework Statement Using the third and fourth of Maxwell’s equation in integral form, show that a plane polarized electromagnetic waves propagates in accordance with the generalized wave equation. Determine the velocity of light in terms of the permeability and permittivity constants...

Homework Statement A loudspeaker at the origin emits sound waves on a day when the speed of sound is 340 m/s. A crest of the wave simultaneously passes listeners at the{xy} coordinates (43 ,0) and (0,33).What are the lowest two possible frequencies of the sound? Homework Equations v(sound)=...

I was looking into propagation of EM waves, and it appears there is an overlooked nuance here. It is often said that EM-waves are self-propagating because a change in the E-field causes a magnetic field nearby, so a constantly changing E-field [i.e. a "vibrating" field] causes a constantly...

A beam of unpolarized light falls upon a polarizer which polarizes the light in e.g. x - direction. After that polarizer, we put another one which polarizes it along the y - direction. Of course, no light is transmited. Now we put a third polarizer between the first two, so that the third one...

Homework Statement Assume a piano has 100 different notes from the lowest to highest. We go up from note to note by the same frequency ratio, say starting at 20 Hz. Assuming that the lowest frequency excites the basilar membrane, 30 mm long, at its end, and that this represents a quarter of a...

I was taught that Huygens's principle is an accurate description of the way light propagates. Something like: "All points along a wave front can be modeled as point-sources for new waves having the same phase and frequency." This appears to be a good model to explain phenomena such as...

I'm working my way (slowly) through Landau & Lif***z Classical Mechanics. I'm finally nearing the end of chapter one, and although I hit another stumbling block, I think I've got it now. If anyone has the time to check my reasoning, I'd be grateful. I will quote the passage that was confusing...

Homework Statement I'm trying to calculate the velocity of propagation of a RG58 cable that is 0.5m long. It is connected to a pulse generator that passes pulses through the cable. The cable is connected to an oscilloscope, which plots the pulses. The period of the pulses are 5 microseconds...

What is the difference of a magnetic and nonmagnetic medium? And how does it affect wave propagation on these mediums?

Homework Statement Consider the points (x, y) = (0,0) and (100,10). Calculate the unit vector u pointing from the first to second. If each coordinate has an uncertainty of +/-2, calculate the uncertainty in u using propagation of error, but making reasonable approximations based on the values...

I have a question about the propagation of light, I am not that technically versed in all the matters involved so it is a philosophical question. The principle of relativity, deducible from Newton's laws, has long been considered verified experimentally, most famously by Michelson-Morley's...

Homework Statement I have completed a lab that uses a Wheatstone bridge to find an unknown resistance utitlizing a resistance box and a slide wire. This will yield the unknown resistance from the following formula... Ru = unknown resistance Rs = known resistance from the resistance...

Hi. I'm not even sure if I'm posting this in the best forum! I'm having a lot of trouble grasping parts of this paper.. Eur Biophys J. 2009 Jun;38(5):637-47. Epub 2009 Mar 4. A nonlinear model of ionic wave propagation along microtubules. Specifically, they use a phase space plot that...

I need to know the propagation velocity of a transverse wave on a long thin bar or rod. In terms of material properties, such as E and density, and in terms of geometry such as I (2nd moment of area). I'm a physics grad, so reasonably versed in such things. But can neither find nor derive...

Hello, if we assume that the wave propagation-speed in a medium is v, does this imply that there is an "upper-bound" for the maximum frequency that a perturbation can produce? Or are these totally unrelated quantities? Thanks!

I'm trying to get an intuitive sense for errors and picked some random numbers: x = 2.5 +/- 0.01 find f(x) = x³ d f(x) / dx = 3x² d f(x) = 3x² dx = 3(2.5)² 0.01 = 0.1875 What I don't get is why f(x - Δx) ≠ f(x) - 0.1875 and why f(x + Δx) ≠ f(x) + 0.1875 Where did I go wrong in...

My doubt arises because I couldn't understand how a Poincaire Sphere gives us info about direction of propagation of wave. Now as we know Poincaire sphere is a neat way of showing the polarization state of an TEM wave. Now ,let me give an example to illustrate my doubt : - Let us take a...

Homework Statement Find the equivalent resistance viewed by A and B and its equivalent uncertainty: http://img707.imageshack.us/img707/5040/dadadadaz.png R1 = 10ohm, 5% tolerance. R2 = 2ohm, 1% tolerance. R3 = 5ohm, 5% tolerance. R4 = 15ohm, 1% tolerance. The Attempt at a Solution...

Hi I've looking into path loss for electromagnetic waves and it's quite straight forward to figure out how it works in free space by looking at the free space path loss formula (http://en.wikipedia.org/wiki/Free-space_path_loss). It has not been that easy figuring out how another medium...

Hi All Is the following statement true: Electromagnetic energy requires a wave medium to propagate. (The way free electrons in a copper conductor transfer energy in an AC circuit. Electrons can act as wave medium). If it is true, How does EM energy travel in space. Can gravity act as a...

Hello everyone. I have tried to do as much research as my layman mind will allow on how an electromagnetic wave propagates in relation to how a sound wave for example does. I understand that an acoustic wave is longitudinal and works on compression and that a light wave is a transverse wave...

We were taught in the vibrations and waves lecture course that the solution to the wave equation for traveling waves is of the form ψ(z,t) = Acos(wt-kz). In the Electromagnestism course we learned that EM waves are traveling waves and have the solution E = E0cos(kz-wt). I know that changing...

erm, ok let's say i have a value, with uncertainty, like y = 10 ± 3 so let's say i multiply y by 2, then it becomes 20 but does the uncertainty becomes 3 x 2 = 6? , hence y = 20±6 ? what about divide? does it becomes 1.5? i roughly understand fractional uncertainty and propagation...

when an electron neutrino is produced in the sun, it have the total energy of E. the total energy E have the relation with mass and momentum as E2=p2+m2. during the journey of its propagation from sun to earth, the electron neutrino change their flavor to muon neutrino which have mass m'...

Homework Statement You have a rubber cord of relaxed length x. It be- haves according to Hooke's law with a "spring con- stant" equal to k. You then stretch the cord so it has a new length equal to 2x. a) Show that a wave will propagate along the cord with speed...

I'm working on trying to understand wave propagation. In particular, I'm trying to understand directional wave propagation in elastic and inelastic materials. Is there an ideal theoretical medium in which it is possible to propagate waves in an entirely directional i.e. straight-line manner...

Homework Statement Consider y_1=Asin(5x)exp(-2t) y_2=Aexp(4ix)exp(-2it) y_3=Asin(2x-5t)exp(-2t) (i)which one represents a wave that propagates at constant speed with no change in its profile (ii)Confirm it satifies the wave equation and obtain the wave velocity (iii)Comment...

Recently I came across an example for working out error propagation, and I'm having trouble following the steps: A = 100 \pm 1% B = 10 \pm 1% AB = (100 \pm 1%).(10 \pm 1%) = \left\{1000 \pm \left[\left(100.1\%\right) \pm \left(10.1\%\right)\right]\right\} // get confused here, how does...