Explain what meant by the refractive index of a material is 1.33

When the refractive index of a material is 1.33, it means two things:

1. Speed of Light: Light travels 1.33 times slower in that material than it does in a vacuum. The speed of light in the material ($v$) is given by $v = \frac{c}{n}$, where $c$ is the speed of light in a vacuum and $n$ is the refractive index. So, in this material, $v = \frac{c}{1.33}$.
2. Bending of Light: When light passes from a vacuum (or air, approximately) into this material, it will bend towards the normal. The higher the refractive index, the more the light bends. A common material with a refractive index of approximately 1.33 is water.