http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/waves/generalwavesrev5.shtml
Source: http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/waves/generalwavesrev5.shtml
Short video introducing the basics of refraction
Source: Mrs G Boyson: http://www.knowmia.com/watch/lesson/45683
A revision video for GCSE science and P1 to describe refraction.
Source: https://youtu.be/QoZA9EwUt-M