Reflection and refraction are two interesting behaviors of waves. They show us how waves react when they meet surfaces or change materials.

Reflection:

• This happens when waves hit a barrier and bounce back.
• The angle at which the wave hits the barrier (called the angle of incidence) is the same as the angle at which it bounces back (called the angle of reflection). We can think of this as $i = r$.

Refraction:

• This is when waves change direction as they move from one material to another.
• When the waves change speed, they start to bend. We can use Snell's Law to explain this, which goes like this: $n_1 \sin(i) = n_2 \sin(r)$.

In short, reflection is all about bouncing off surfaces, while refraction is about bending as waves move through different materials.