In QM a photon with wavelength comparable to the width of a slit, will pass through and create a 'Gaussian Distribution' on a screen. As the slit width is decreased (gets thinner), the 'GD' on the screen will counterintuitively INCREASE (aka. widen). My question is it possible that the slit wall thicknesses themselves are the cause of this effect? How does slit wall thickness effect the GD on the screen when all other variable are held constant?