When light moves through different materials, it can do a few interesting things:

1. Reflection: About 4% of the light bounces back when it hits smooth surfaces. It reflects at the same angle it came in.

2. Refraction: This is when light bends. It bends because it changes speed when moving from one material to another.

   • There's a rule called Snell's Law that helps us understand this bending: $n_1 \sin(\theta_1) = n_2 \sin(\theta_2)$.
   • For example, light travels super fast, about $3.0 \times 10^8 \, m/s$, when it's in a vacuum (empty space). But when it goes into glass, it slows down to around $2.3 \times 10^8 \, m/s$. This shows that glass has a value called "n" that is about 1.33.

3. Diffraction: This happens when light waves spread out after going through small openings. How much they spread depends on the size of the opening compared to the wavelength of the light.