h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Entry: Interferometry - Not Technical - A3553085
Author: paudie - U704629

This, I hope, is a non technical desription on how interferometry works. It should aid you in understanding the other interferometry experiments I have submitted.

In leaving out the technical parts, you seem to have left out a description of the purpose of the equipment. It's not just to make a pretty pattern on the screen, is it?

Is it correct to say that mirror M1 is mounted on arm 2 while mirror M2 is mounted on arm 3. Would it not make more sense to call the mirror on arm 2 "M2" and call the one on arm 3 "M3"?

Won't all the light have to be of the same frequency? Does this mean that you have to use a laser beam?

The basic shape of an interferometer is A cross" (coz, being inanimate objects, I don't think they exhibit any emotions!)

I've only skimmed this so far.

Be back later.

"Being inanimate objects, I don't think they exhibit any emotions!"

What a charming misrelated construction!

TRiG.

I though I did explain, it's used to show the wave nature of light. You don't have to use a laser just a light that is all of the same frequency. It only works if the light is the same frequency, so that if one of the mirrors is moved the phase of the light is changed so interference occurs. If you want to know about experiments using the interferometer check my other entries.
I thought that I'd post this as helper to the other interferometry entries.

Thanks for the feedback, and apologies to those who think that interferometers are angry all the time.

I see you have added this to explain other entries, but I feel that this would need to 'stand alone' as an entry as well. It needs some explanation of what it is used for to give it some context; if this means a little overlapping with other entries, so be it. It's an interesting entry, but without explaining what it is used for it feels a bit empty. It's like having an entry on a steering wheel without explaining why you would need one to drive a car. Just a paragraph would do.

Speaking as a non-scientist, this is good work and just needs a bit of polishing. Well done!

Spectroscopy! Ah at last something I have an inkling about.

This is a good explanation of the basics but, like the previous reply, I think it would look more "complete" with a paragraph on FT-NIR or Mid IR applications?

Although keeping that simple is the challenge, especially if you get into the matrix algebra of PLS calibration modelling of the data

sorry ed out there for a minute

Are you still working on this Paudie?

not really
I know I have some tidying up to do, but I had exams and just started a new job, so I've been a bit tied up. Thanks for the interest though. It should be completed soon. I hope.

How's this one going, paudy?

I'm not sure what else needs to be changed. I can understand it because I wrote it. So I just need your opinions on what to change. Thanks for the interest.

Anyone who a) understands these things and/or b) is interested in these things...what do they feel Paudie needs to do to this?

Same goes for the other inferomentry entry he's written.



Kat

As someone who knows nothing about the subject, here is what I think could be done:

The definition of what a nanometre is would be better as a footnote.

A diagram would help - can you draw one or get someone else to draw one?

Some links would be good - are there any entries on light or mirrors you could link to?

That's something to be getting on with

Looks like elvis is on his way out of the building....

Agreed. I assume you have an ultra-organised list

Yup, but some of these aren't quite eligible yet, so I will wait and send the list in when they are, next week.

I'm just not sure how else to change it. Same goes for the other entry. Ah well it was worth a try.

You're still here!!!

Did you do the things Cyzaki mentioned?

We're currently going through PeerReview weeding out seriously elvised etc entries so we *should* be left just with entries that deserve and need comment. Hopefully this will force people to return here.

Just noticed this. It's good but I vehemently agree that it needs some context; it doesn't feel like a standalone entry. Some other inputs:

Also the very purpose of the thing should be mentioned up front, i.e. to amplify tiny variations in length to detectable levels, presumably.

Are they always in the shape of a cross? Of the few examples I'm aware of, laser gyros are triangular with three arms, and the LIGO gravity-wave detector is a big "L" shape with two arms.

Typo "uesually"

You should mention that the coherent light source is *usually* a laser, otherwise a load of people will say "oh, he means a laser, why didn't he say so?", like I did.

In the description, you say that it is the change in position of mirror M2 that causes the phase shift. This seems to me peculiar to a very specific application: to measure the position of the mirror very precisely, and doesn't really explain how the interferemeter could be used to measure anything else. In a gyro the entire device moves as one and it is the change in relative position of the beam, which continues in a straight line, that is detected. Also I believe in the Michelson-Morley experiment the mirrors were static and the earth moved?