Medium Definition and 365 Threads

The Maxwell's equations in vacuum leads to the wave equations for the fields of the form \nabla^2 \vec E = \frac{1}{c^2} \frac{\partial ^2 \vec E}{\partial t^2} (the same for the magnetic field) Such equations are Lorentz-invariant. Let's consider now the electromagnetic field in a...

Hello all, I already know that the radiant intensity of a point light source falls off with the inverse square of the distance to the source. This, however, only happens in a vacuum. My question is, what is the more general law for a point source inside an opaque medium with a known...

Hi Folks, After a general search online, I have not yet found a simple description of refraction in a medium with an inhomogeneous refractive index. For example: if we have a block of glass with a beam of light shining through it, and the block has a gradient in the real part of the...

Hello! My book here states that for a medium where the index of refraction n increases with increasing frequency (or wavenumber), "the group velocity is less than the phase velocity". This is stated for a wave which is the sum of two waves with equal amplitude and differing frequency...

We know that light travels at the same speed in vacuum regardless of the observer.And light also travels at a speed of c/n in the medium.My question is since c/n is the limit speed in medium,then do we have the similar Lorentz transformation in the medium which just replace c with c/n? For...

I am trying to find the differences between electric cables designed for High voltage, medium voltage and low voltage electric transport, but I am failing to find an answer. I was wondering if you could help me with this. I know that aluminum is almost always the metal of choice, thicker is...

If vibrating object produces sound in air and there's a solid object in front of it after some distance, will those sound waves(which were propagating in air before) start propagating within that same solid object or reflected or absorbed or etc. Please explain also. Thanks.

Homework Statement This is just my doubt and not really a question. We know that speed of light changes upon change in medium of propagation. Its wavelength also changes. But its frequency doesn't change. So, does the colour of light change upon change in the medium of propagation...

Homework Statement the laws of refraction and reflection are the same for sound as for light. the speed of sound is 340 m/s in air and 1510 m/s in water. if a sound wave traveling in air approaches a plane water surface at an angle of incidence 12°, what is the angle of refraction? Homework...

For example can massless particles serve as media?

I was told In a post in another thread that EMR needs a solid media for its transmission. Therefore if the aether exists it must be a non flowing solid. If this is correct then how is it possible for light to be transmitted through air and water?

Hey. I am a freshman in high school, and iv'e been reading about building a cyclotron. I have the basic principles understood but can someone explain how exactly i would assemble on, and the mathematics behind it. ALso and information about how the fields interact would be phenomenal. I have...

So, I have been doing a lot of reading. I have an 8 year old girl that has renewed my interest in physics, chemistry, biology, etc. I find it interesting that we say that Electromagnetic Waves travel through a vacum. We know that mechanical waves like those propagated in liquids and gas...

Hello experts! I have 2 questions. 1)Difference between dispersive and non-dispersive medium. 2)ω=\sqrt{\frac{4β}{m}}sin\frac{Ka}{2} is a relation for dispersive medium. How to reduce it to non-dispersive relation? Here is some math work I have performed to reduce it to non-dispersive...

What is a linear medium?

I'm an Indian student who is interested in pursuing a life and career in Physics. Recently, I was browsing through the site of the Niels Bohr Institute in Copenhagen. But I was disappointed to know what they don't offer Bachelor level courses in English language! So I'd like to know of such...

Homework Statement I know that for air, the intrinsic impedance η is 377 Ω, but it becomes complex in a conductive medium. This fact is sort of hindering me in being able to answer a few problems consisting of electric and magnetic waves in a conductive medium, but I just wanted to clarify one...

What is the relationship (a mathematical one) between the density and the refractive index of a medium?

Hi, Before I phrase my question, I'll just go through what I know so no unnecessary comments happen. I've read that the speed of light slows down in a medium because when a photon hits an electron the electron absorbs the energy of the photon and re-emits another photon. I also know...

Homework Statement Consider an isotropic medium with constant conductivity \sigma. There is no free charge present, that is, \rho = 0. a)What are the appropriate Maxwell equations for this medium? b)Derive the damped wave equation for the electric field in the medium. Assume Ohm's...

I just got this question on a classical mechanics assignment... and unfortunately I know NOTHING about dielectric materials (never been introduced to me for some reason >.<). I don't even know why this is on my classical mechanics assignment but it is anyway. And btw there is a disclaimer on the...

If light scatters when propagating through (example) water then why does it appear to travel in straight lines. Yes, i know pencils appear broken but the overall impression is of straight line focused light propagation, and that does not make sense to me from a 'scattering' point of view. If...

Homework Statement A dipole p is situated at thecentre of a spherical cavity of radius a in an infiite medium of relative permitivity \epsilon_r . show that the potential in the dielectric medium is the same as would be produced by a dipole p' immersed in a continuous dielectric, where...

Homework Statement The polarization charge in the surface of a spherical cavity is -\sigma_e \cos\theta ,at a point whose radius from the centre makes and angle \theta with a give axis Oz. Prove that the field strength at the centre is \frac{ \sigma_e}{3 \sigma_e} parallel to Oz. If the...

Hello, I have a problem understanding wave propagation in dispersive medium because the prescription to solve the wave equation for electromagnetics waves is this : a) suppose \mu,\epsilon are function of frequency only b) solve the wave equation...

i mean i know particles move up and down but i want to go into a bit more detail.consider a constant fequency wave passing thru a rope.now what i want to know is that when the wave passes do all the particles bcome crest and trough turn by turn or do some specific particles (those which bcame...

\GammaHomework Statement if an electric field is traveling in air and hits a medium n2. then there will be three fields present: the incident electric field the reflected electric field and the transmitted electric field. the electric field in medium 1 would be...

I am walking at 2 metre/sec and light, from a flashlight behind me, is moving at 1 m/s. So my eyeballs are catching up with the photons ahead of me. Do I see the flashlight? Do backward photons look strange? Are they red-shifted, blue-shifted? Assume my optics have been replaced with...

Homework Statement This is from hand and finch. We proved in the previous problem that (using euler lagrange equation): x=\int_0^y\frac{dy}{\sqrt{\left(\frac{n[y]}{n_0}\right)-1}} where n_0 is the refractive index at y=0 and x=0. The ray enters horizontally. As an actual computation...

In the context of electromagnetic wave propagation in ferromagnetic medium, what is meant by magnetostatic spin wave? This terminology one came across in the wave modulation in ferromagnetic medium. Thanks in well advance..

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...

if in a capacitor ,the dielectric medium is replace by higher dielectric constant material the how does the capacitance of capacitor vary and why? thanks.

hi ... when a ray of light passes through a medium of some refractive index, then due to cancellation of electric fields the speed of light reduces inside the medium as compared to air. with this thought in mind, can we say that, as the speed of light has got reduced , there is something...

G'day all, I was just wondering why light bends when it enters a different medium. I understand that the light slows down, but why exactly do all the photons, waves or whatever swing around like a gate? Intiutively, I would assume that they would all just slow down and speed back up once...

First off, please do not direct me to: https://www.physicsforums.com/showthread.php?t=104715 topic number 4 because i have read, read again, and then read once more and i am getting nowhere with that. Can you please just address these points: Does light slow down because of the...

Is the Gravitational force between the two bodies depend upon the medium between them?and is the gravitaional force is quantized?

Can electricity be transmitted using Concentrated beams without using wires with no energy lost in the process?

My answer is: it is the relationship between the angle of incidence and the angle of refraction. Is it correct? If not, what should be the correct answer?

Homework Statement 2 parallel rays are traveling in a medium of refractive index 4/3. One of the rays passes through a parallel glass slab of thickness t and refractive index 3/2. What will be the path differnce between the two rays due to the glass slab? The Attempt at a Solution The...

A study of the motion of a relativistic continuous medium http://www.springerlink.com/content/j8kr55831h411365/

Homework Statement I have tried to solve the displacement sideways of an lightray through a medium with snells law. The question is how much does the ray travel in x-direction in the new medium with width D. It says in the text that one should use pytagoras but I can't seem to understand...

A photon goes from vacuum into a medium. This causes its momentum to reduce. Hence by the de Broglie formula, its wavelength should increase. But, since the refractive index of the medium is greater than 1, and n_2/n_1 = \lambda_1 / \lambda_2 , and hence, its wavelength should decrease...

Homework Statement ~ Homework Equations integration The Attempt at a Solution for a) i use linear density and calculate the mass of circumference and integrate it bottom to top. is it riight?any other methods? for b) i use surface density and calcuate the mass of disk and...

Does the superposition principle for wave equations (say electromagnetic) hold also for non homogeneous and anisotropic media? I.e. can one always represent a wave traveling in an arbitrary direction as a sum of waves propagating along the principal axes of, e.g. dielectric tensor \epsilon_{ik}...

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

hi the airy disk equation is d= 1.22 lambda / NA my question is: lambda is the wavelength in medium or in vacuum? thanks in advance

Let us consider Maxwell's equations in a homogeneous isotropic medium. We may look for a set of transformations for which the form of the equations remain unchanged[in accordance with the first postulate of Relativity].Of course we get the same Lorentz transformations but with a different value...

How do I calculate for velocity of a falling object through any medium at any given time if I have to consider both buoyancy and viscous drag. If I consider Newtons law , I assume that it would be something like m(dv/dt)=Fnet =mg-Drag-Buoyant force Am I supposed to get a...

Homework Statement A projectile enters a resisting medium at x=0 with an initial velocity v0=900ft/s and travels 4in before coming to rest. Assuming that the velocity of the projectile is defined by the relation v=v0-kx, where v is expressed in ft/s and x is in feet, determine (a) the...

When light enters into a denser medium,its velocity decreases.I can understand it is due to the optical density.But when the light again comes out of the denser medium,how does it regain its speed(i.e velocity of light).