So let's understand the brain waves before I go into the correlation between the brain waves and hypnosis.
Beta- the awake consciousness reasoning wave. Our dominant normal waking state wave. These brain waves are important for critical thinking, heightened alertness, effective functioning and logic. You are awake and alert.
Alpha- the deep relaxation wave. This wave is present when you slip into a daydream, or in a light meditation. You are calm and have an inward focus.
Theta- the deep meditation and sleeping wave. This wave is present during light sleep or deep meditation. This is where you may experience vivid visualizations, great inspiration, profound creativity and insight. It acts as a gateway to learning and memory. It is not uncommon to also feel a deep spiritual connection. You are conscious of your surroundings but your body is so deeply relaxed. This is an optimal time to program the mind using hypnosis as well.
Delta- the deep sleep wave. These brain waves are slow. Here, your awareness is somewhat detached. You are in a dreamless deep sleep, which is essential for the body to heal and regenerate.
During hypnosis, the brain waves will start with beta as you are focused and fully alert, then as you become more rested and relaxed you will have more alpha wave patterns. After the induction there is an increase in theta waves. As therapeutic suggestions are given the brain waves will vary depending on how deep you go, and the nature of the suggestions. Generally, they will go between theta and delta. As termination begins you will exhibit alpha waves, and finally back to beta activity.