Recent content by Soren

no you are right, r is called the specific refractivity of the substance. I suppose that is what they are trying to tell me, that specific refractivity (r) does not depend on density, whereas the refractive index of a substance does.

I must be stupid but my textbook states that the refractive index of a media does not depend on the density according to the Lorentz-Lorenz formula (LL) (\frac{n^2-1}{n^2+2}) = \frac{4\pi Ne^2}{ 3m} \frac{1}{\omega_0^2 \omega^2} Specifically it (Physical Optics, Akhmanov Nikitin pp.367) says...

Ah, yes. I have similar example in my textbook, however, as I understand this then the temperature (or concentration) imposed on the radius =R does not vary with time, i.e. it is constant for t>0. I think your latter suggestion that simulates a pulse is interesting, although I am unsure how to...

This is exactly what I have been trying to "look up" and it does not exist, at least I cannot find it.

Yes, I am aware that setting the initial concentration to be evenly distributed over r and z, and ignoring the convective dispersion is a big simplification (I am aware of taylor-aris dispersion) But because of the dimensions, the velocity and time that the flow is switched on, I believe that at...

So I have read up a bit on the subject. I want to find a solution for fick's second law of diffusion in my described problem (see attached pdf). In brief it is diffusion from the walls of a tube into the bulk solution. First step is to make sure that I have the proper initial and boundary...

Thank you Chet - this answers my question. On a further note I am actually looking into the differential equations (unsteady diffusion in finite medium actually) and may have further qestions, do you have experience with these?

I'm not looking for a numerical solution, I'm just trying to understand. I was looking at a case with a strictly laminar pipeflow (i.e. circular geometry). For such a flow the mean velocity (u) =Q/ pi*x^2, with x being the diameter and Q the flowrate = u/pi*x^2. Now if I have two fluid inlets...

From the best of my knowledge, no frequency does not change. However, the amplitude would change if the reflection coefficient was <1. Frequency of light is a property of the refractive index and can go up and down depending on the media it is propagating.

The diffusion distance for a Brownian particle is given as x^2 = 2Dt D: diffusion coeficient, t: time However, not all textbooks include the factor 2 (i.e. they just write x^2=DT). Is there a difference or are they just beeing sloppy? I run into trouble when I want to calculate the length of a...