In this video I explain why the light slows down in different materials and how the speed of light never actually changes
See 3Blue1Brown’s video here:
Looking Glass Universe Videos:
Harvard video: https://youtu.be/57s60mlapCc?si=LNn20f8qsT_xqISO
Online Simulators I used in this video:
https://www.compadre.org/osp/EJSS/4030/138.htm