Let the light rays fall on a surface at an angle.
Normally, light wave or rays are refracted or reflected in the
directions known by the laws.
Scattering of light is the
deviation of the light waves from directions of usual reflection and
refraction. Light waves or rays are scattered in all possible directions
with varying intensities.
The molecules of the medium in the path of light absorb light (energy) and re-radiate in all possible directions.
When the size of the objects (particles) on which the light waves are incident is comparable to the wavelength, then scattering is very high and is inversely proportional to 4th power of wavelength. So red light is scattered the least.
Scattering depends also on the refractive index of the medium (optical density) or speed of light in the medium. If the medium is gas or air, then it depends on the density or molecular concentration. If the medium is a solid and the surface is very smooth then scattering is very less from that surface. Scattering is more from a rough surface.
Scattering of light may also depend on whether light waves are polarized or not.
Intensity of light or amount of light scattered in a direction depends on the angle of scattering.