A TV station broadcasts the same program to a neighborhood 30 km away. Viewers can receive it either as analog TV or digital TV. A thunderstorm increases interference (lower SNR) and nearby buildings cause multipath reflections. What difference would viewers most likely observe as interference increases?
- Analog TV stays perfect until a threshold, then suddenly becomes completely unwatchable, while digital TV slowly adds more "snow."
- Analog TV shows gradually increasing snow/ghosting as interference rises, while digital TV tends to look clear until it suddenly pixelates/freezes or drops out (cliff effect). (correct answer)
- Digital TV always has more static than analog because binary signals are more sensitive to noise at all levels.
- Analog TV can correct bit errors caused by reflections, so it remains clearer than digital TV during storms.
Explanation: This question tests understanding of how digital and analog transmission methods perform differently under realistic conditions like noise, interference, and multipath in TV broadcasting. The fundamental difference in transmission performance is that analog signals have noise add directly at every stage (cable, amplifier, relay) with no way to distinguish signal from noise, causing gradual quality degradation proportional to noise level, while digital signals only need to distinguish between two levels (0 and 1), allowing regeneration at repeaters—the receiver detects whether each pulse is closer to 0 or 1 and creates a fresh, clean pulse, effectively removing accumulated noise and maintaining quality over long distances. In a noisy environment with increasing interference and multipath, analog signals degrade as attenuation reduces amplitude and noise adds to signal, requiring amplification that also amplifies noise, causing signal-to-noise ratio (SNR) to worsen with each stage until signal is buried in hiss/static/snow, while digital signals maintain quality because regeneration at regular intervals detects the 0s and 1s and recreates perfect pulses, allowing transmission over long distances with essentially no quality loss, and error detection/correction algorithms can identify and fix bit errors that do occur, providing reliable delivery even when channel conditions are poor; for gradual noise increase, analog quality smoothly degrades (slight hiss → loud static as noise increases), while digital maintains perfect quality until noise exceeds the threshold where receiver can't reliably distinguish 0 from 1, then suddenly fails with dropouts or complete loss (cliff effect). Choice B is correct because it correctly explains cliff effect (digital) vs gradual degradation (analog). Choice A is wrong because it reverses the degradation patterns, claiming analog has cliff effect or digital degrades gradually. Practical implications: virtually all modern long-distance communication uses digital (internet, cell phones, satellite, fiber optic cables, digital TV/radio) specifically because regeneration and error correction provide reliable transmission over vast distances despite noise and interference—analog dominated historically when electronics were simpler, but digital's advantages (quality maintenance, error handling, compression, encryption, computer compatibility) led to digital revolution in telecommunications. The trade-off is complexity (digital requires encoding/decoding, analog is direct) but performance benefits overwhelmingly favor digital for any application requiring transmission over distance, multiple copies, or integration with computers, which is why analog transmission is largely obsolete except in legacy systems and niche applications.