In many transparent materials, dispersion causes differentcolors(wavelengths) of light to travel at different speeds. Thiscancause problems in fiber-optic communications systems wherepulsesof light must travel very long distances in glass. Assuming afiberis made of silicate crown glass (see figure below), calculatethedifference in travel times that two short pulses of light taketotravel 15.4 km in the fiber if the firstpulse has a wavelength of700 nm and the second pulse has awavelength of 500 nm.
