Final answer:
The high frequency used in facial treatments and medical diagnostics that involves high rates of oscillation is known as ultrasound. Ultrasound in therapeutic treatments is often referred to as ultrasound diathermy.
Step-by-step explanation:
The high frequency currently used for facial treatments characterized by high rates of oscillation is known as ultrasound. This frequency is much higher than the highest frequency that humans can hear. Ultrasound utilizes high-frequency sound waves to generate images, which is similar to how it is used in medical diagnostics, such as observing a fetus in the womb. An example of its use in treatments is ultrasound diathermy, which applies frequencies typically ranging from 0.8 to 1 MHz to provide deep-heat treatments for therapeutic purposes.