A surface is considered smooth if the size of irregularities is small
relative to the wavelength. Otherwise, it is considered to be rough.
Electromagnetic waves are diffracted around intervening objects. If the object
is small relative to the wavelength, it has very little effect. The wave will
pass around the object undisturbed. However, if the object is large a shadow
will appear behind the object and a significant amount of energy is reflected
back toward the source. If the object is about the same size as the wavelength,
things become quite complicated, and interesting diffraction patterns appear.
Use the interactive activity to calculate and graphically display the
angle of refraction for different angles of incidence and different materials.
Radio waves also bend when entering different materials. This can be
very important when analyzing propagation in the atmosphere. It is not very
significant in WLANs, but it is included here, as part of a general background
for the behavior of electromagnetic waves.