What OSI physical layer term describes the physical medium that uses the propagation of light?

• A. fiber-optic cable
• B. latency
• C. throughput
• D. goodput

Answer: (A)

Fiber-optic cable is the physical medium that uses light to carry signals. In the physical layer, the focus is on the actual media and signaling methods, and fiber-optic cables transmit data as light pulses, delivering very high bandwidth over long distances and resisting electrical interference. The other terms describe performance, not the medium: latency is the delay in delivering a bit, throughput is the raw data rate, and goodput is the useful payload rate after overhead. So fiber-optic cable best fits the description.