  We investigate statistical distributions of differences in
gravitational-lensing deflections between two light rays, the so-called lensing
excursion angles. A probability distribution function of the lensing excursion
angles, which plays a key role in estimates of lensing effects on angular
clustering of objects (such as galaxies, QSOs and also the CMB temperature
map), is known to consist of two components; a Gaussian core and an exponential
tail. We use numerical gravitational-lensing experiments in a Lambda-CDM
cosmology for quantifying these two components. We especially focus on the
physical processes responsible for generating those two components. We develop
a simple empirical model for the exponential tail which allows us to explore
its origin. We find that the tail is generated by the coherent lensing scatter
by massive halos with M>10^14h^-1Msun at z<1 and that its exponential shape
arises due to the exponential cut-off of the halo mass function at that mass
range. On scales larger than 1 arc minute, the tail does not have a practical
influence on the lensing effects on the angular clustering. Our model predicts
that the coherent scatter may have non-negligible effects on angular clustering
at sub-arcminute scales.
