refract

 
Pronunciation: /rɪˈfrakt/

verb

[with object]
  • (of water, air, or glass) make (a ray of light) change direction when it enters at an angle: the rays of light are refracted by the material of the lens
  • measure the focusing characteristics of (an eye) or of the eyes of (someone): when refracting patients an ophthalmologist relies on verbal reports

Origin:

early 17th century: from Latin refract- 'broken up', from the verb refringere, from re- 'back' + frangere 'to break'