room topic changed to Interferometry: Chat room for John Rennie and Guru Vishnu [mathematics] [physics]

@JohnRennie: Hi sir :-)

@GuruVishnu hi :-)

@JohnRennie Are you free now, sir?

@GuruVishnu ish ... I'm doing some routine checks on servers.

@JohnRennie Fine sir. Could you ping me once you're done?

(removed)

@GuruVishnu pingggggggggggg

@JohnRennie :-)

@GuruVishnu hi

@JohnRennie: I asked the following question on the main site, yesterday. If possible, could you answer it sir? So far, I haven't received any comments or answers.

I think he's just saying that the shape of the $\mu(\nu)$ curve is roughly similar for all materials.

Or I guess it would be better to use $\mu(\nu)-1$ since that's centred around $n=1$.

@JohnRennie I don't think so sir. We could see the range of refractive indices for a material increases with increase in mean index value.

i.e. for some material $A$ we can approximately write $\mu_A(\nu)-1 = a(\mu(\nu)-1)$ for some constant $a$.

@GuruVishnu that diagram shows only a fraction of the whole curve.

The whole curve will look a bit like this:

Still I don't get what you're explaining sir. I think according to "larger the mean deviation, larger will be the angular dispersion", a prism made of SF10 deviates more as well as disperses more and a prism made of FK51A deviates less as well as disperses less. I'm just asking is it possible to have a prism made of some Material X which deviates more but disperses less, sir.

@JohnRennie Again that same image from your answer! :-)

The bit of the graph in your image comes from the left edge of my diagram i.e. at frequencies much lower than the resonant frequency.

@JohnRennie Yes sir. Got it. It's just horizontally flipped.

Yes. The point is that the graph looks roughly like this for all materials. The only differences are the resonant frequency and the overall amplitude.

@GuruVishnu yes because your graph has wavelength on the x axis not frequency.

Fine sir. I hope you read the following message:

Now I get what you're explaining. Neglect that initial comment sir.

Anyhow, the point is that if the graph is the same shape for all materials then the ratio of the refractive index to the gradient will be the same for all materials.

@JohnRennie So, Material X is simply not possible?

I think material X is unlikely. I'm not sure I'd say it is impossible, because the shape of the curve is only roughly the same for all materials.

@JohnRennie Ok sir. If you had said it's impossible, I was ready to ask is there any fundamental law which prevents its existence like I did for "real and erect" images.

The shape of the curve is kind of universal because it's basically measuring the polarisibility, and that always increases as you get near the resonance. You get the same shape curve in mechanical systems as well as optical ones. I think we talked about this.

The shape is the same for any resonant damped system.

So basically it's always true that $\mu \propto d\mu/d\nu$.

@JohnRennie I understood that for the mechanical resonance. And I remember you were telling that it's almost similar. That was just a few days ago :-)

But I wouldn't swear that there couldn't be some weird system where other effects dominate. That's why I said mostly true.

@JohnRennie Fine sir. Let me assume Material X is so far not invented (for the time being). Thank you sir :-)

@JohnRennie: Just now saw your answer sir. I'm going to read that now :-)

Thank you sir :-)

@GuruVishnu it's what we've already discussed here, but I thought I'd post it as an answer for completeness.

@JohnRennie Yes sir. I noticed that. After our discussion, I thought of asking you for an answer. I almost typed the message, but I thought whether it's right or wrong. However, it was quite surprising when I saw your answer. I imagined to have your answer there and I have it now!

:-)

Just now posted a question on mirascopes.

Good night sir :-)

Bye :-)