[math-fun] Low-tech measurement of the wavelength of light
I once read about an experiment where you can measure the wavelength of light using a drop of oil and a pond. The idea is that the oil will disperse into a uniform film whose thickness (calculable as the volume of the drop divided by the surface area of the pond) is close to the frequency of visible light, and then you can observe chromatic effects. Can anyone provide a reference? I did a Google search but couldn't find the thing I recall reading. Thanks, Jim Propp
Hi Jim, Do you mean thin film interference? https://en.m.wikipedia.org/wiki/Thin-film_interference There are many ways to measure wavelength though, especially if you are talking about monochromatic light. You can use cds/dvds/Blu-ray discs to do something like the thin slit experiment, and another option is to use polarizing filters and measure birefringence: https://physlab.lums.edu.pk/images/3/30/Cellophane2.pdf —Brad
On Apr 11, 2020, at 11:18 AM, James Propp <jamespropp@gmail.com> wrote:
I once read about an experiment where you can measure the wavelength of light using a drop of oil and a pond. The idea is that the oil will disperse into a uniform film whose thickness (calculable as the volume of the drop divided by the surface area of the pond) is close to the frequency of visible light, and then you can observe chromatic effects. Can anyone provide a reference? I did a Google search but couldn't find the thing I recall reading.
Thanks,
Jim Propp _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
The accepted interpretation appears rather to be that one measures the diameter of the oil molecules, assuming the wavelength of light. I googled << measure the wavelength of light using a drop of oil and a pond >> and got a page-ful (?!) of hits --- eg. http://physics.princeton.edu/~steinh/ph115/Lab_2_final_2014.pdf << Ben Franklin, who started all this, publishing an account in 1774, used a pond and olive oil. >> http://d1068036.site.myhosting.com/eChem.f/labP1-thickness.html WFL On 4/11/20, James Propp <jamespropp@gmail.com> wrote:
I once read about an experiment where you can measure the wavelength of light using a drop of oil and a pond. The idea is that the oil will disperse into a uniform film whose thickness (calculable as the volume of the drop divided by the surface area of the pond) is close to the frequency of visible light, and then you can observe chromatic effects. Can anyone provide a reference? I did a Google search but couldn't find the thing I recall reading.
Thanks,
Jim Propp _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
Also Newton’s Rings: https://en.wikipedia.org/wiki/Newton%27s_rings <https://en.wikipedia.org/wiki/Newton's_rings> …which showed that the visible spectrum ranges over a ratio of about a major sixth, as opposed to an octave as Newton thought. (I learned this from Peter Pesic’s wonderful book Music and the Making of Modern Science.)
On Apr 11, 2020, at 10:17 AM, James Propp <jamespropp@gmail.com> wrote:
I once read about an experiment where you can measure the wavelength of light using a drop of oil and a pond. The idea is that the oil will disperse into a uniform film whose thickness (calculable as the volume of the drop divided by the surface area of the pond) is close to the frequency of visible light, and then you can observe chromatic effects. Can anyone provide a reference? I did a Google search but couldn't find the thing I recall reading.
Thanks,
Jim Propp _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
Cris Moore moore@santafe.edu "It is bound to be very imperfect. But I think it possible that I have got my statues against the sky.” — Virginia Woolf
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James Propp