![Diagram showing the refraction of light in water.](http://static.sciencelearn.org.nz/images/images/000/000/049/full/Refraction-of-light-in-water20150805-30610-expmepedited.png?1674163623)
When light travels from air into water, it slows down, causing it to change direction slightly. This change of direction is called refraction. When light enters a more dense substance (higher refractive index), it ‘bends’ more towards the normal line.