Wikipedia says (link) that in the limit of many interfering waves the distribution of intensities (which go as the square of the vector's length) becomes exponential $${\textstyle P(I)={\frac {1}{\langle I\rangle }}\exp \left(-\frac{I}{\langle I\rangle}\right)},$$ where $$\langle I\rangle$$ is the mean intensity.