# Physics EE: Newton's rings

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Hello everyone,

I'm having a bit of a crisis here with my Physics EE. Despite being given more than enough time to do my extended essay, I now find myself in big trouble only one week before the final deadline. The reason for this, aside from me being a terrible procrastinator, is that I discovered only today that the results from my experiment are completely useless. Not only that, but I'm also lacking a proper research question.

Now writing 4000 words in just a few days won't be a problem on its own, but unless I can quickly figure out a research question and redo my experiment I simply won't have anything to write about. So I'm really hoping I could get some help from here.

My original topic had to do with finding out the thickness of thin (oil) films by measuring interference in them. That turned out to be a pretty impossible topic before I could even get to any experimenting, so instead I ended up measuring the spectrum at different points in Newton's rings produced by white light (well not white light, but continuous spectrum anyway). The phenomenon of Newton's rings is of course pretty simple, but it seems that pretty much all experiments on Newton's rings are being done with monochromatic light and not white light, so I still think this can potentially be a source for an adequate topic.

Anyway, in August I went to the university (I needed a Newton's rings apparatus for my experiment) to make some measurements, and although I didn't have a specific research question I got some pretty good-looking results and I thought I could easily figure out what to concentrate on with my essay. So for a long time I thought I had results where could see the minimums and maximums of different wavelengths spaced out nice and evenly (as could be expected in thin-film interference) – actually the person helping me at the uni thought so too when he saw my measurements. Once I finally started working on the actual essay a week or two ago, I started wondering why the wavelengths at which these maximums occurred weren't really changing much for different points in the pattern. I still wasn't really worried as I thought there would be a reasonable explanation for this – and turns out there was. It's just that it wasn't the kind of explanation I was expecting...

Basically my supervisor, when I finally showed him my results today, realised that all the minimums and maximums visible in my graphs are most likely in fact from the spectrum of my light source and not the interference. (Yes, I really felt pretty stupid after hearing that.) I really hadn't even thought about this possibility since I had measured the spectrum of the light from a point with no interference – but now that I think of, it the intensity must have simply been too low for the spectrometer to get any proper measurements from it.

So, I'm now pretty much left with nothing here. My supervisor isn't of much help either as he told me that he can't really do anything for me before I come up with a research question – and he is of course right. It's just that I'm kind of running out of ideas with a phenomenon this simple as there aren't that many possibilities.

I'm pretty sure I could modify the experiment and get some kind of results, and since it seems like a somewhat original experiment I'm hoping that my EE isn't completely doomed. The question remains, what could possibly be my research question? If I can in fact get the constructed/destructed wavelengths visible in my measurements (I'm quite confident that it is possible) there would be at least something for me to write about, but I don't quite see how to formulate a "sharply focused" research question out of that. So I would really appreciate any suggestions you might have.

In any case, thank you if you took the time to read all this. I wouldn't be surprised if this post turned out to be longer than what my EE is right now...

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However, I think this is a great idea. but why don't you make it a bit simpler than this. I heard a lot that the simpler the experiment the better. Well in your case it is not simple as we are not going to study in depth in theory or experimentally in the IB HL course. However, this means you can do it as an EE.

I have some ideas about it, if you may consider, which I think they are simple and can be done:

1- To investigate the dependency of the Newton’s rings on the wavelength of the light ht by illuminating with monochromatic light from a metal spectrum.

2- determine the radius of curvature at given wavelengths or you can use a specific light from a metal spectrum for eg. yello form the sodium spectrum.

I hope this is useful...

But I guess you will have to the experiments again. However, there are not hard to. maybe one day experimenting and getting the result. Then you will have to write the theory in the EE and insert your results and explaining them.

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Thank you for you answer, it really cheered me up quite a bit simply to see somebody trying to help me out.

I have previously considered both of the topics you suggested, however I'm wondering if they are a bit too simple? Even though none of it is in the syllabus, those two experiments are probably the two most common ones related to Newton's rings and designs about them can be found all over the Internet and textbooks. So although simple experiments are encouraged, I'm worried that might be just too... basic? I mean it's probably not good if your design is among the first things that comes up when you google "Newton's rings"?

I actually started off in August by taking measurements of rings produced with two different lasers (known wavelengths), so I would have already something to start with. But I'm really not sure whether it's okay to go with something that simple?

Edited by Satmi

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I don't think its too simple..

If you check most of the Extended Essays you see most of them are already done. Actually all of them, except some of them is a bit complicated.

However, this one is not simple. They are not asking for something new. And only collage people who are doing this only. So I think there is no problem with it.

Also check with your supervisor and you will get a better feedback about them. He might be interested. Remember simple ones are much likely to get you an A or a B

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Okay, you're probably right. That would certainly make things much easier for me – I'll talk to my supervisor about this tomorrow and hopefully he'll agree. Thanks a lot for your help.

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I talked to my supervisor today and while he agreed that it would be best to go with a simple experiment, he said that there is a limit as to how simple the topic can be and basically if your method is the first thing that comes up in Google when you search your topic it just won't be enough. Or that I might pass with that, but I can't expect any decent grade.

I could only talk to him briefly today, so it probably won't be until tomorrow that I'll decide on my topic and research question. So good suggestions are still welcome. I'm not sure how I can find the time for doing the experiment, but my supervisor promised to talk to the IB coordinator about my situation. The deadline is an internal one after all, and in the previous years students have been allowed to make some changes to their EEs even after that if absolutely necessary. We'll see...

Edited by Satmi

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I know you will find some in google. However, won't the different metal affect it.

I mean they will be doing different metals in Google and you can choose another metal...

If you are stuck, I prefer you do it in your first language

Edited by MR.AHM

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