Medium Definition and 390 Threads

Is the relation v_{\varphi }v_{g}=v^{2}=\frac{1}{\mu \varepsilon } always true in a plasma ? Where v_{\varphi }, v_{g} are respectively the phase and group velocity of the electromagnetic wave that is propagating in the plasma.

I have no doubt that someone, someone somewhere has tried this. but if you take a 10 WAT output from a argon beam and run it through a Rubie Active medium chamber I would expect that the light would be excited to a higher range. Am I in error?

Visible light propagates at less than c in water. What about other wavelengths of EM? Do they all travel at the same reduced speed? I think not, but am not sure. If they travel at different speeds then Suzanna can be seen comin' round the mountain in certain wavelengths before others.

My question is as follows: Does the focal length of a concave lens change when put into a medium such as water? Initially the focal length of the lens is 20 cm in air. Would it get larger or small in water?

In this thread Antiphon had written that When I first encountered that, I thought there's something wrong with that, but could not figure it out. In order to create a current the electron must flow from one place to another. But in EM radiation although the electron oscillates or jiggles, it...

Homework Statement Consider the waveform shown below heading towards a boundary between two strings. Let string 1 have mass per unit length of µ1 = 0.05 kg/m and let string 2 have a mass per unit length µ2 = 0.02 kg/m. Let the tension in both strings be T = 100N. --> ____/\____ _ _...

So, I've read here http://en.wikipedia.org/wiki/Interstellar_medium that the Interstellar medium varies greatly throughout space. Of the categories listed; Molecular clouds, Warm Neutral Medium, Clound Neutral Medium, Warm Ionized Medium, H II regions, and Coronal Gas/Hot Ionized Medium...

Hi all. I am asking for some help with getting a physical intuition for the following situation: Consider an observer and source, at rest. The source emits sound waves of a particular frequency, 'f'. Letting the medium (air for example) between the source and the observer move with a particular...

Hello everybody, I'm focusing on the description of the coupling of a monochromatic short EM wave and on the description of the energy absorption by matter. The problem is the following. It is well-known that the Poynting theorem in a non-dispersive medium considers the variation of...

Dear Forum members I have a question regarding the stratton-chu integral to calculate the farfield radiation pattern from a dipole. The theory works very well for the homogeneous medium, i.e if the emitter can be considered to be embedded in a homogenous medium. My question is if it is...

Hello all, I want to that would there be any harm in placing a medium voltage switchgear adjacent to low voltage motor control system ? what are the possible side effects ? if any pls share, if u agree , pls share that too !

I was tutoring a student in an optics lesson the other day. We discussed the foundational concept, that light travels more slowly in a physical medium (such as air, water, or glass) than in vacuum. She asked, "Why? Because of friction?" and I said, "No, not friction," but then I had to admit...

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...

Homework Statement Suppose an object of mass .505 kg was oscillating with initial Emec = 1.12 J at the end of a spring, and the system was submersed in a liquid medium that absorbed energy at a steady rate of .250 m2/s * spring constant (29.6 N/m). How long would it take the spring to stop...

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! I've been searching this on the internet but found no relevant results, so maybe one of you can help me. How are essential oils and their properties affected by the very alkaline medium during soap-making? I suppose some of their components are lost, some remain, but in what...

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?

[SOLVED] I have got the answer. Answer is 40cm. --------- Homework Statement Focal length of thin lens in air is 10 cm.now medium of one side of lens is replaced by medium of refractive index μ=2.the radius of curvature of lens with contact with the medium is 20cm. Find the new focal...

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...