In most cases, you do not need an in-depth knowledge of physics for clinical psychology. Clinical psychology is primarily concerned with the assessment, diagnosis, and treatment of mental health disorders and emotional difficulties in individuals. As such, it is rooted in the field of psychology and relies more on concepts from biology, neuroscience, and social sciences rather than physics.
The core subjects you will need to focus on for clinical psychology are psychology itself, human development, abnormal psychology, counseling and psychotherapy techniques, psychological assessment, research methods, and ethics in psychology.
However, while physics may not be directly relevant to clinical psychology, having a well-rounded education is beneficial in many ways. Knowledge of diverse subjects can enhance critical thinking, problem-solving skills, and your ability to understand the broader context of psychological issues. Furthermore, being knowledgeable in various disciplines can also help you connect with clients who might have diverse interests or backgrounds.
Ultimately, if your goal is to pursue clinical psychology, it is crucial to focus on psychology-related coursework and training. Physics is not a necessary requirement, but it doesn't hurt to have a general understanding of different fields.