State Snell's law of refraction and copy and complete the diagram.

Here's the solution for question 8. (a):

8. (a) (i) State Snell's law of refraction.

Snell's law states that for a given pair of media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant. This constant is equal to the refractive index of the second medium with respect to the first.
Mathematically, it is expressed as:

$$\frac{\sin i}{\sin r} = n$$

where $i$ is the angle of incidence, $r$ is the angle of refraction, and $n$ is the refractive index.

**8. (a) (ii) Copy and complete the