3.17 REFRACTION

:: AIR HAS LOW DENSITY
:: GLASS HAS A HIGHER DENSITY THAN AIR

when light moves from an area of low density (air) to an area of higher density (glass), the light ray bends towards the normal, and the opposite when the light ray moves from an area of high density (glass) to an area of low density (air) the light ray bends away from the normal.
the bending of light rays when it moves through a medium to another is called refraction.

low density -----> high density = bends towards normal
high density -----> low density = bends away from normal