Ko te whakapikonga o tētahi hihi aho ina whakawhiti taua hihi mai i tētahi whaitua pūataata ki tētahi. Hei tauira, ka hakoko te hihi aho, e whakawhiti ana mai i te hau takiwā ki te wai. Ka hakoko te hihi aho nā te mea he pōturi ake te ngaru aho i roto i te wai, tēnā i te hau takiwā.
The bending of a ray of light when that ray passes from one transparent medium to another. For example, a ray of light bends when travelling from air into water. It bends because the light wave travels slower in water than it does in air.