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When I closely look at the side of one of my fingers with one eye, I see:

enter image description here

From a closer distance, it somewhat looks like this:

enter image description here

The white-gray lines (in fact their color is also cream) are much narrower in reality (I can very hardly see the second one). I have doubt whether this is the result of a diffraction (my eye pupil playing the role of a small hole or slit) or the result of some sort of parallax caused by the diameter of the pupil (which is about 6mm).

Things get more complicated when I hold two of my fingers close to each other, then I see:

enter image description here

With a closer look, it's like:

enter image description here

In fact only the middle line can be seen properly if the fingers aren't close enough to my eye. Some say that this is the result of interference (the space between fingers playing the role of a narrow slit); but it seems like this has something to do with the lines of each finger (photo #1) like the lines of each finger somehow add up, like in the photo below for the diffracted light of two stars:

star light diffraction

S.Shahsiah
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  • You mean you do not believe those guys where you copied the photos. Well, diffraction does not add in a simple way. you may check this and the link there in. – mikuszefski Nov 10 '16 at 16:26
  • Also check the knife edge effect – mikuszefski Nov 10 '16 at 16:28
  • @mikuszefski I didn't actually disagree with them, I simply had doubt (I edited the body to show my doubt!). Also I didn't say that they add in a simple way; I just said that they might somehow add up like in the photo of stars. (Btw I only copied one photo from them :) ) – S.Shahsiah Nov 10 '16 at 16:40
  • @S.Shahsiah then please post credit where due. Otherwise you might be violating copyrights – docscience Nov 10 '16 at 16:43
  • @docscience You're absolutely right. I just took a photo of my own fingers :-) – S.Shahsiah Nov 10 '16 at 16:56
  • Something else to consider is that visible white light spans roughly an octave, so there won't be much apparent diffraction. Try it with red light because its more monochromatic, and it has the longer wavelength. – Digiproc Nov 10 '16 at 17:13
  • @Digiproc I tried what you said and it didn't make any difference. Then I realized that since X∝, (X is the distance of a fringe from the center) therefore ∆X∝∆∝100nm; therefore the wavelength difference can't have an observable effect – S.Shahsiah Nov 10 '16 at 17:35
  • Sure, was only one photo, but making your own is definitively better. The problem of diffraction and interference is that they do not "add" in a simple way. Its due to their wave nature, causing them to appear in the first place. Surely the effect of having the fringes on one edge is related to the lines you see if you have a slit, and from their wave nature they add, but the simple lines you see don't. – mikuszefski Nov 11 '16 at 08:17

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