The device that splits up white light into its constituent colors is called a prism.

Here's how it works:

* Refraction: When white light enters a prism, it slows down and bends. Different colors of light travel at slightly different speeds through the prism. This difference in speed causes the colors to bend at slightly different angles, separating the white light into a spectrum of colors.

* Dispersion: This process of separating light into its different colors is called dispersion.

Let me know if you'd like to know more about prisms or the process of light dispersion!