noun (n)

• the change in direction of a propagating wave (light or sound) when passing from one medium to another(noun.phenomenon)

  source: wordnet30
• the amount by which a propagating wave is bent(noun.event)

  Synonym:
  deflection, deflexion
  

  source: wordnet30
• The act of refracting, or the state of being refracted.(noun)

  source: webster1913