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/sci/ - Science & Math

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10231661 No.10231661 [Reply] [Original]

I'm sorry bros but can someone please help me. Despite me and my partner being top students, very hard working and so on the supervisor just can't be arsed and doesn't turn up to answer questions or explain what we're meant to be doing.

I'm doing a project where the mass of Rubidium is determined from readings from a photodiode connected to an oscilloscope, and the values got were underestimates. This is expected, apparently "due to the 3 overlapping Gaussians on the oscilloscope". I've tried asking him what he means and he just repeats "the 3 gaussians" over and over again. It looks like the left pic.

What actually does he mean?

>> No.10231663
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10231663

>>10231661
Sorry wrong pic

>> No.10231665

>>10231663
I think it may be due to the 3 overlapping gaussians

>> No.10231685
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10231685

>>10231665
epic

Also to everyone, I know what a Gaussian is I just have no idea why there's meant to be 3. The laser goes through the rubidium sample and is detected on a photoodiode, as shown

>> No.10231785

>>10231661
you mean you’re measuring the abundance of different isotopes?

>> No.10231826

>>10231661
you're not explaining your setup or instruments properly. Wavelength/linewidth of laser? Pulse rate? Oscilloscope specs? "due to the 3 overlapping Gaussians on the oscilloscope" is a meaningless statement, so unless this is a bad translation there's not much we can do with it.

>> No.10231828

>>10231785
I'm sorry if I worded it like a retard. It's a physics experiment, we are determining the mass of the isotopes. I'm sure it's something simple he means and don't want to waste everyones time trying to work it out

>> No.10231840

>>10231826
Wavelength is 780nm, don't know linewidth we haven't and it's not on the laser/manuals. Haven't been told the pulse rate either and not been supplied with manuals. It is a custom made laser so not on internet.

Oscilloscope is a digital 2 channel oscilloscope, although without wanting to sound rude I don't know why this would matter. If I'm being honest though, we have barely got through it maybe cause we're just shit maybe cause we've had to practically do it alone so our knowledge is lacking a bit

>so unless this is a bad translation there's not much we can do with it.
he is foreign which has made the whole thing very difficult. I swear this must be something simple that we're just not getting. We've completed the experiment and are writing up, but need to explain the underestimate.

>> No.10231844

>>10231826
Our best guess is that the "3 overlapping gaussians" lead to the gaussians on the oscilloscope being widened. This makes sense as the equation from which mass is calculated is inversely proportional to the standard deviation of the Gaussian on the oscilloscope

>> No.10233530

>>10231685
>>10231663
I see two bells. Those are not really gaussians, they are more Maxwell curves since gaussian gives a total integral value of 1. Maxwell curves are also a bit more slender and have more linearity on the sides and is associated with emittance and absorbance. I assume you are doing an absorbance experiemnt.
I say try expanding the oscilloscope view, maybe there is another curve a bit off to the right.
On the second oscilloscope view I am seeing some emittance spikes, some contamination perhaps? Also this is a bit old school kind of spectroscopy, I am more expeienced with instrumental spectroscopy, spark OES and XRF.