fading

Fading is the gradual loss of strength, brightness, or prominence of a property over time or distance. It occurs in natural processes as well as human-made systems, and the causes, manifestations, and remedies vary by context.

In communications and signal processing, fading refers to fluctuations in signal amplitude and quality as it propagates through a medium. Effects such as multipath propagation, Doppler shift, and shadowing cause the received signal to vary over time and frequency. Types include slow fading and fast fading, as well as flat fading and frequency-selective fading. Common models use scenarios like Rayleigh or Rician distributions to describe the statistical behavior of the signal. Mitigation strategies include diversity techniques (such as multiple antennas), adaptive modulation and coding, power control, and equalization to maintain reliability and reduce error rates.

In color and material science, fading denotes the loss of color intensity or pigment stability under exposure to light, heat, humidity, or chemical factors. Ultraviolet radiation is a major driver of photo-fading in textiles, plastics, artwork, and printed materials. Protective measures include UV absorbers or stabilizers, protective coatings, and minimizing exposure or storing materials in controlled conditions.

In psychology and education, fading is a learning technique in which prompts or assistance are gradually removed to promote independent performance. It supports the transfer of control from the trainer to the natural cue by systematically reducing prompts according to a planned schedule.

In film and audio production, a fade describes a gradual transition in which an image or sound becomes progressively brighter or louder or fades to silence, used to signal movement between scenes or states.