Final answer:
The fiber-optic media uses an insulator, as it employs glass or plastic fibers to transmit light signals, and these materials act as insulators allowing light to transmit through via refraction and total internal reflection.
Step-by-step explanation:
The media that uses an insulator is d) Fiber-optic. Fiber-optic cables use glass or plastic fibers for the transmission of light signals, which carry data. These fibers are insulating materials that allow light to travel through them via refraction and total internal reflection. To ensure the most efficient transmission of light, fiber-optic cables often have varying refractive indices, where the core has a higher index than the cladding, which acts as an insulator and keeps the light within the core. In contrast, coaxial cables and twisted pair cables use metallic conductors and are not primarily insulators, while satellite communication does not involve insulating materials in the same way fiber optics do.
Additionally, it's important to address the information given:
- True - High-voltage wires are indeed insulated to prevent electrical losses and safety hazards.
- True - Refraction is useful in fiber-optic cables as it allows for the guidance of light signals over long distances without significant loss.