Medium Definition and 390 Threads

Somewhere in our Galaxy resides a cloud of neutral hydrogen gas with a radius of 10 pc. The gas density is 10^7 atoms/m^3. (a)How many 21-cm photons does the cloud emit every second? (b)If the cloud is 100 pc from the Sun, what is the energy flux of this radiation (in W/m^2) at the Sun...

Homework Statement a) Assuming the presence of sources (J flux density) and (p charge density) , write out Maxwell’s equations in the time domain in terms of and only for a lossless, but inhomogenous medium in which ε = ε(r) , μ = μ(r). b) Derive the vector differential...

Homework Statement Light travels at different speed through different materials. If it travels at speed c1 in a medium of refractive index 1.2, what is its speed in a medium of refractive index 1.6 a. 1.3 c1 b. 0.67 c1 c. 2 c1 d. 1.7 c1 e. 0.55 c1 Homework Equations n=\frac{c}{v}...

In what medium do light, energy, and matter exist? I'm wondering what medium, material, substance do light, energy, and matter exist in. I'm not saying that I neccesarily think there is one, but I am wondering what the theories are in relation to our universe. Do these three things exist in...

An electromagnetic field, as a plane wave, has a known space-time dependence: E = E0cos(ωt-kx). In a transparent medium it is the same except for involving the refraction indices n. Now, let us look at the field in a moving reference frame - that with v = c/n. What solution is for the...

Let's say the speed of light in a medium is c'. Assume that the medium itself is moving at a very high speed v (close to c). What is the speed of light in the moving medium if a. light and medium are moving in the same direction. b. opposite direction (can the speed be zero or negative?) c...

A little question which I thought of today. I thought about what happened in a medium with Lorentz transformation. With a refraction index n, the speed of light is altered to c/n. However, as far as I can see now this shouldn't influence the Lorentztransformations, right? It's tempting to put...

Cr2O7(-2) + HNO2 + H(+) --> Cr(+3) + NO3(-) + H2O The question asks me to balance the above rxn, and then say what the coefficient in front of H2O is. The answer key says it's 4, but I've tried three times and I keep getting 6. I've always had trouble with these, so chances are I'm doing...

I can't find a solution to these questions. Can someone help? 1. An algorithm to determine if a Sudoku puzzle is easy, medium, hard, or evil. 2. For every valid Sudoku puzzle, there exist at least one valid solution. True or false? Proof?

I have heard that the speed of light remains c even if it is not in a vacuum. the light bounces around in the substance a bit, so light appears to have slowed down. Is this true?

Hello, I have a question regarding page 241 of “Principles of Electrodynamics” by Melvin Schwartz. He is deriving the electric field inside a conducting medium as a function of position z; by summing the incident field, contributions from slices of material to the left of z, and from slices...

I know from my physics course that sound has a particular speed in any medium that it is traveling through, much like light. I have not learned, however, why this is so. I know that sound is simply a pressure wave traveling through air (or water or steel or whatever), but it doesn't seem...

I was reading a paper on yeast two hybrid, and I was wondering why a bait protein and GAL4 activation domain show growth on Leu- medium. I thought there should be no interaction since there is no prey protein?

In case of anisotropic medium the energy is flowing in a different direction with respect to the direction of light propagation .How can it possible ? If so,then in what form the energy is flowing ? How can I detect that energy is flowing in a different direction not the direction of light...

Could someone please explain how the speed of light, a supposed constant, can be slowed down in a medium? I checked Wikipedia and all they had to offer was this "In passing through materials, the observed speed of light differs from c. When light enters materials its energy is absorbed. In...

Homework Statement The critical angle of refraction for calcite is 68.4 (degrees) when it forms a boundary with water. Use this information to determine the speed of light in calcite. Homework Equations n=c/v n= Index of refraction c= Speed of light in a vacuum v= Speed of light in...

http://www.physlink.com/estore/cart/Hydro-Clock.cfm I think it just uses the fluid as a medium to transfer electricity from an internal battery, my friends aren't so sure. Any thoughts on this out there?

I am studying Poynting vectors. I run into question that I don't see any good explanation in all the books I have. All the books claimed E_{(z,t)} =E_{(z=0)} Re[e_{j(wt-\beta z)} + \Gamma e_{j(wt+\beta z)}] But sinse E0 is complex so this is what I have and is not equal to what the...

This has always puzzled me and nobody (professors, textbooks) ever seemed to elaborate on it (maybe it is very simple and I merely didn't catch on). Anyway, I understand that when a wave passes through a medium, the individual particles of the medium are briefly displaced from their...

Don't know if this is the correct forum. While we know that light's phase velocity in a linear medium with refration index n is c/n, what can we say about signal's velocity? If I switch on a laser inside the medium (let's say glass) at t = 0, when will the first photon arrive to a detector...

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

If we have a body traveling through a foam or fizz, then how does one measure mach-number or reynolds-number in a foamy/fizzy medium? What are the mechanics under this regime? Presumably, a foam or fizz is not a true static homogenous fluid medium. Perhaps for simplicity, we could assume...

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...

hello guys, I finally decided to join a forum online and starting asking my " brilliant" :-0 questions..hehehe..oh man i have plenty of those.. OK, am reading the book: understanding physics, by isac asimov. And i am reading about magnetisim now, and its stated two things that bugged my...

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