A wave front radiating from a smooth surface will be smooth at first. Points, where the wave front looses its smoothness belong to the caustic. Move with the mouse over the picture to see the radiation. The formula below produces tables of equal width
if a n = a - n , a 2 m =0, nonzero m and a 1 =0. A two dimensional parameter domain a 0 =4.0, a n =0 for n different from 0,3,5 can be explored to the left by moving with the mouse over it.