I have a long tube (aout 30 cm) with a convex lens of diameter 7.5 cm on the one end and a small hole of diameter 2 cm on the other. When i shine a light through the hole and let it pass through the lens, i get a flowery pattern on the wall, looked very strange to me. There is a maxima in the center as expected, then dark for a little further and then patches of light all around the center that resemble petals. Why is this pattern formed? Note: This pattern does not appear to form without an apperture smaller than the lens, like a hole.