Noisy Wave Pattern Between Round Objects Behind a Light

[Jarvis323]

I noticed that if I hold two small rounded quartz stones together in front of my eye, with light shining on them from the other direction, I see what looks like a very distinct, black, noisy waveform between them. Does anyone know the detsals about wy this happens?

 

[sophiecentaur]

This sounds like a diffraction effect. You can get the same result in the gaps between the knuckles of your fingers. The trick is to look in there distance and not directly at your fingers. That gives a better effect. This hyper physics link gives an image of the illumination across the slit. With a slit, this will actually appear as a set of parallel lines. For two balls, the spacing varies so the lines will not be parallel and the image is more complicated.