The profile of Saturn's ring a as derived from stellar occultations

Stellar occultations behind Saturn's ring A reveal sharp-edged gaps in its outer parts. Observed fluctuations in stellar brightness during one observation can be interpreted as Fresnel's diffraction zones. According to this the sharpness of the edges of the gap are estimated to be under 700 m, which also means that the thickness of ring A in that part cannot exceed a few hundred metres. A further conclusion is that particle size must be a lot less than a few hundred metres.