Final answer:
The main advantage of a stop action permanent wave in physics is that it allows for precise timing and control of wave patterns.
Step-by-step explanation:
The main advantage of a stop action permanent wave in physics is that it allows for precise timing and control of wave patterns. Stop action refers to the ability to freeze or stop the wave at any point, which is achieved by applying a fixing lotion or an oxidizing agent to the hair. This technique is commonly used in permanent wave treatments to ensure that the desired wave pattern is achieved.