"Snell’s law, or the law of refraction, explains the light passing through a boundary between different media such as water, glass and air. When a straight piece is placed into water, it appears to be bending where it touches the water surface.
An optical fibre is a transparent light guiding, or wave guiding pipe made out of extruded silica or plastic. It transmits the light between the two ends of the pipe. Light is kept inside the core by total internal reflection.
Paraffin oil is a transparent liquid that is commonly used in cosmetics and medicinal purposes. It is a highly refined form of mineral oil which is a by-product of the distillation of petroleum. Mineral oil is also commonly used in industries as thermal fluid in electric components due to its non-conductivity."