Light behaves differently depending on the material it travels through. The speed of light is fastest in a vacuum (empty space) and slows down when it enters denser mediums like air, liquids, and solids. This is because the refractive index, a measure of how much light bends, is higher in denser materials. So, denser materials like solids have the slowest light speed. Scattering occurs when light interacts with particles in a medium, causing the light to deviate from its straight path. This scattering creates beautiful effects like the red sky at sunrise/sunset. Cathode rays are streams of electrons emitted from a negatively charged electrode (cathode) in a vacuum tube. They travel towards the positively charged electrode (anode) due to the voltage difference.