Movie of waves being deflected towards regions of lower phase velocity.
We are so used to seeing waves behave in a certain way that we usually don’t stop and think about why waves behave the way they behave.
Imagine a headland with not-very-steep slopes, and wave crests approaching it. Consider now two possible scenarios. In the first one, the wave crests bend around the headland almost as to embrace it. In the second one, wave crests bend away to channel the energy through the deeper waters around it. Which one will it be?
The only difference between those scenarios is that in one case waves are being refracted towards regions of lower velocities and in the other towards regions of higher velocities.