Last week I performed Young's double slit experiment using a laser. As expected, I obtained an interference pattern as predicted by Fraunhofer theory (enveloped by the 1 slit diffraction curve). Then, I added two polarizers with perpendicular axes in front of each slit. Since the light coming from the slits had now different polarizations, I no longer noticed the interference pattern (only the diffraction from each separate slit).
It is generally known that in order to perform Young's double slit experiment using natural light, we should first make the natural light "more" coherent by placing a single slit before the double slit. However, from my understanding, natural light is unpolarized. So now my question is, why does natural light produce an interference pattern if the incoming light in unpolarized? Shouldn't the light from the 2 slits not interfere because the polarizations are different just like in the laser experiment? Does the first slit polarize the light? Or is it that the light exiting the 2 slits is synchronously unpolarized (the electric field vectors are always on the same line) hence creating a pattern?