ray tracing techniques can be applied to study light scattering by spherical and non-spherical particles under the condition that the size of a particle is much larger than the wavelength of light. the light can be considered as collection of separate rays with width of rays much larger than the wavelength but smaller than a particle. rays hitting the particle undergoes reflection, refraction and diffraction. these rays exit in various directions with different amplitudes and phases. such ray tracing techniques are used to describe optical phenomena such as rainbow of halo on hexagonal ice crystals for large particles.