The
Golden Gate Bridge in
San Francisco, California, as
refracted through
rain drops on the window of an
automobile, which act as
lenses. In
optics, refraction occurs when
light waves travel from a medium with a given
refractive index to a medium with another, whereupon the wave's
phase velocity is altered, causing the wave to change direction; its
wavelength increases or decreases but its
frequency remains constant.Photo credit: Mila Zinkova