Multiple choice general knowledge science & technology Which of these are proper brain waves Theta Reta Uncha Speta Reveal answer Fill a bubble to check yourself A Correct answer Explanation Theta waves (4-8 Hz) are one of the five main types of brain waves, along with delta, alpha, beta, and gamma waves. They occur during drowsiness, meditation, and REM sleep. 'Reta', 'Uncha', and 'Speta' are not real brain wave types.