Medium Definition and 365 Threads

Homework Statement How can I find out if a medium is dispersive or not, only with its wave equation? Homework Equations The Attempt at a Solution

Hello all! I'm studying for my final, and I'm trying to figure out my teacher's method for the following problem. Could you help me out? A plane wave is propagating in free space with a frequency of 10 GHz. The amplitude of the electric field in the x-direction is Ex = 2 V m-1. (ii) Find...

I' ve read that the CMB could be emitted by intergalactic medium. What about it?

as I understand it aether theory claims that fields are strain in an elastic medium. the elastic medium can be thought of as a system of springs and masses. (note that the springs store energy proportional to the square of their change in length) I can see how this probably works fine for...

1. The motion of a body falling from rest in a resistive medium is dv/dt = Bv - Av^2. 2. Find it's initial acceleration. Find the velocity at which the acceleration becomes zero. 3. B and A are constants. dv/dt = acceleration = Bv - Av^2. vf = vi + at vf = 0 + Bv - Av^2(t) vf...

1. The motion of a body falling from rest in a resistive medium is dv/dt = Bv - Av^2. 2. Find it's initial acceleration. Find the velocity at which the acceleration becomes zero. 3. B and A are constants. dv/dt = acceleration = Bv - Av^2. vf = vi + at vf = 0 + Bv - Av^2(t)...

ok, ill try to explain myself as best as i can. you have a box with all walls with "perfect mirrors", remove all air, then force light into the box. assuming no light escapes would the "density" become great enough for sound to use the light as a medium to travell through. i hope explained...

Homework Statement Two vibrating sources emit waves in the same elastic medium. 2. Problem This is just the beginning part of a question that goes into detail about speed, reflection, refraction, and angles of incidence. All of which I understand, but as usual, the easiest part of the...

Hello, Quick question. If space doesn't have, or consist of, an medium (ether?) would that mean space is infinitely small and large?

FAQ - "Do Photons Move Slower in a Solid Medium?" I have a question regarding this post in the FAQ's: My question is, to what extent is the above applicable to photons moving through a liquid medium? Do the atoms and molecules that form a liquid also lose their individual identity and form...

I can formulate the problem as follows: Assume that the vacuum is multidimensional excitable medium. We want to prove or reject this statement. The simplest way to reject is to find any fact (phenomenon or property of the world) which contradicts the assumption. I can assume some...

I'm a materials engineering junior-to-be(yay summer), and like most material scientists i just kind of assume things I don't really understand when it comes to physics =P But I was pondering about refractive indexes today and... Well, WHY does light slow down in a medium? The refractive...

a lot of transformation laws have c in them. the speed of light, however, depends on the medium ( c' ) and is different from the c in vaccuum. so my question is, which one should i use in relativistic laws if the medium is , say, water with c' = \frac{c}{1.33} of course one would say c...

I have a project that i am doing that requires that i pump methanol at a temperature of about 140F at a volume of about 1 to 2 gpm and a pressure of around 150 - 200 psi. It must be capable of 'run dry' by which i mean that it may not always have fluid to pump. Can anyone give me a lead on a...

do velocity of light changes in hot or cold medium(air or water)...if it changes,wat is the reason for that change...wat effect the temperature of medium has on velocity of light?

Hi i am a senior that needs helps as soon as possible since its due TOMORROW! My problem is that I have to adress interference and medium in the use of drums

1.A rectangular loop and a Circular loop are moving out of a uniform magnetic field to a field free region with a constant velocity V.In which loop the induced e.m.f is constant during the motion of the loop. 2.Name two Physical quantifies other than velocity,wavelength and C,associated with...

I have read the sticky topic (FAQ of Physics Forums), concretely the topic https://www.physicsforums.com/showpost.php?p=899393&postcount=4" five or six time, and I would ask you about this part: How it is re-emitted, when it is not first absorbed?

Light travels from medium C to medium D. The angle of incidence is larger than the angle of refraction. Which medium has the lower index of refraction? Explain your logic.

Another thing that I've never really understood... As fas as I'm concerned, waves need a medium to travel through, but electromagnetic waves seem not to need one at all. I just can't visualise them as oscillations in anything. It sort of helps if I visualise EM waves as photons, because then...

Light in a vacuum has momentum \hbar k but when the light enters a dielectric medium, fx. glass, the momentum of the light is increased to \hbar\sqrt{\epsilon} k, where \epsilon is the dielectric constant of the dielectric. Where does the extra momentum come from? How can this be in accordance...

I understand that the speed of light in different mediums (like water) is slower than that of light in a vaccume. I've also read about some expiriments done in which light had been slowed down to a quite imaginable speed, like 70 Km/h. What causes light to slow down in such instances? Is it just...

The speed of light in a vacuum is c in all inertial frames. What about in a medium? Light in a superfluid can be slowed to a few miles per hour, so if this speed was the same for all inertial observers, relativistic effects would be very noticeable on an everyday speed-scale. This doesn't...

Hi, I need to find a book where the problem of the subject is treated. (I am assuming that charge is being fed to the wire by an external source, so as to keep it constant) Does anybody know a reference where this problem is treated? I have looked for an answer in the classical textbooks...

Hi..when light goes from one medium to other medium (like air to glass or glass to air) its velocity changes(either increases or decreases)..if velocity is changing then frequency or wavelength should also be changing..i want to know which one changes..frequency or wavelength or both... I think...

A 11.00 kg object starting from rest falls through a viscous medium and experiences a resistive force R = -bv, where v is the velocity of the object. The object reaches one half its terminal speed in 5.84 s. (a) Determine the terminal speed. 82.7 m/s (b) At what time is the speed of the object...

Hey, can anybody tell me what the estimate is on the mean mass of a particle in the interstellar medium? I would guess around 1-10 proton masses?

as the waves travel through a medium, they lose velocity, however the frequency is constant right? thanks

[b]1.Find the speed of light in the following in m/s... (a) water (n = 1.33) (b) diamond (n = 2.42) (c) quartz (n = 1.54) i can't seem to get any of these right...

Homework Statement In the case of total internal reflection, show that the average rate of energy transport across the boundary is zero. Homework Equations None Provided The Attempt at a Solution All that I have come to is that I should use some form of the following method to find...

Why does the Lagrangian density for the EM field in a dielectric medium take the form d^3 \bf x \left[ \epsilon \bf E^2 - \bf B^2 \right]? I can see that the expression for Lagrangian density has units of energy per unit volume as you would expect but that's about it. Much appreciated.

Show that the action integral for the electromagnetic field in a matter with dielectric constant \epsilon is given by S_m=\frac{1}{8 \pi} \int dt d^3 \bf x \left[ \epsilon \bf E^2 - \bf B^2 \right] where the standard expressions for the E field and B field E=-\frac{1}{c}\partial_t \bf A -...

If everywhere in the universe is at above 0 degrees Kelvin, then there must be some degree of heat everywhere, so this could be considered a universal medium or not, and if what I heard about the sound of the big bang still reverberating throughout the universe is correct (see my contribution to...

I don´t understand how sound propogates. Is this also an inconsistent medium throughout the universe and could a ship be translated on sound stages? Is the sound from the big bang also inconsistant throughout the universe and if it isn´t and other aspects of sound vary throughout the...

here's the problem: 2 vibrating sources emit waves in the same elastic medium. the first source has a frequency of 25 hz, while the frequency of the secound source is 75 hx. waves from the first source have a wavelength of 6 m. they reflect from a barrier back into the original medium, with an...

I'm attempting to calculate the above, but I'm stuck. What I have thus far: intensity is the time average of the poynting vector, where the poynting vector is the cross product of the E and B fields. Using the given expressions, I get: \frac{\sqrt{a^2 + b^2}}{\mu \omega} E_0^2 \exp(-2bz)...

Hi all. First post and all that, so I hope I don't do anything wrong, and that if I do, you'll cut me a little slack :P Anyway, onto the question I'm wanting help with: A J-shock in a Herbig-Haro object is propagating through neutral hydrogen gas at speed 100km/s. The gas has number...

When light travels from a less optically dense medium to a more optically dense medium, the refracted ray bends toward the normal (i.e. air -> water). The reverse is true when traveling from a less optically dense medium to a more optically dense medium. Now... why is this? Why does a...

we have a non magnetic but anisotropic dielectric medium which has the following relationships between D and E Dx = k1*Ex, Dy = k2*Ey, Dz = k3*Ez we have to show that waves propogate in the z-dir'n at one speed only. I can't get the wave eq'n to fall out. Usually you just use...

In the text I use for class, the examples and derivations for functions showing the neutron flux at some point, are all about sources within infinite mediums. Now I have a probelm where I must show that neutron flux, for a point source within a finite sphere, is found by the following equation...

The information given is that a wave is sent though a wire with the frequency of 200 hz, and tarvles 500 m/s. A lighter witre is attached and the wave slows down to 400 m/s. Is it a higher or lighter medium? I want to say lighter as the wavelength is decreeased, meaning it has a figher...

I'm trying to create a model of the procedure of having a bone marrow biopsy done in order to seek ways of eliminating the pain which one has to endure during this process. I'll need to start with modeling fluid flow in a porous medium but this is something I've never done before and have never...

Through what medium does EM propagate in "empty" space? Einstein stated in his Leyden address (1926, I think) that an EM ether was mandatory for the transmission of EM waves through "empty" space. He was unable to reconcile this with the dynamical gravitational ether that had to exist to make...

When a ray of light travels from an optically denser medium to a rarer one such that the angle of incidence equals the critical angle, then the refracted ray grazes the interface. Now, will the principle of reversibility of light work in this case? If yes, please explain.

The fact that light has a smaller apparent speed in a transparent medium can be explained classically by considering the motion of the electrons of the medium in the oscillating (radiation) electric field produced by the source. Because they accelerate, these electrons emit an electric field...

How will it bend? Or will it not bend at all?

Second Postulate Of Special Relativity: "Speed of light in vacuum remains same for all inertial reference frames" The speed of light in glass is 2 x 10^8 m/s . So how is now the above postulate applicable?...Is it true that if one was sitting inside the glass slab , he would see the light's...

That is interesting ST. How dense is the inter-galactic-cluster medium? Garth

If current densities are given in a perfect dielectric medium having \epsilon , \mu I have to find the power dissipated per unit volume, the electric field energy density, and the magnetic field energy density everywhere. Can I get help with equations?

Ok, I don't want no equations and stuff please. :smile: When light travels through a medium the photons are absorbed by atoms in the medium and then a photon is given off by the atom of similar energy, etc, this is correct? If this is so does that mean when I look out the window that I'm...