Refraction of light
Physics Narrative for 11-14
Light changing media
Supposing a beam of light travels through air and meets a glass block.
If the beam meets the glass block straight-on, at right angles, it continues on its path through the glass. If you think that this is hardly a surprising event, you'd be right. You're probably very familiar with the fact that light can travel through glass.
However, rather stranger things start happening if the light beam meets the block at some other angle. In this case the beam of light does not travel straight on, but changes direction as it passes into and out of the glass.
This change in direction is referred to as the refraction of light.