During which sleep phase are alpha waves typically observed?

Alpha waves are typically observed when a person is awake and relaxed, particularly when they are in a calm state with their eyes closed but not yet asleep. These brain waves have a frequency of 8 to 12 Hz and are associated with a state of relaxation and readiness for sleep.

In contrast, during REM sleep, the brain exhibits a different pattern with low amplitude mixed frequency waves, resembling the wake state but characterized by rapid eye movements and vivid dreaming. NREM Stage 1 is the transition phase between wakefulness and sleep where theta waves start to emerge, indicating light sleep. NREM Stage 2 is characterized by sleep spindles and K-complexes, which indicate deeper sleep than Stage 1, and it lacks the alpha waves present during wakefulness.

Thus, the presence of alpha waves distinctly identifies the awake state where relaxation occurs, making it the correct choice.