What is Happening?
he speed of light is a constant for any given media. But different media can have different speeds of light. This is what causes light rays to “bend” when they pass from one material to another. Think of air and glass. They have different speeds of light and that is what make glasses and magnifying glasses work. It also allows glass to appear to disappear when placed in a liquid with the same speed of light as the glass. Pyrex and Wesson oil have very nearly the same index of refraction (ratio of the speed of light in a vacuum to the speed of light in the media).