Ultrasound Physics II Practice Exam

Frame rate and time per frame are reciprocal quantities. Frame rate is how many frames are produced each second, while time per frame is how long one frame lasts in seconds (or milliseconds). Because one frame every second is the inverse of how long each frame lasts, they are inversely proportional: fps = 1 / t_frame. For example, at 60 frames per second, each frame lasts about 1/60 second (≈16.7 ms). If you increase to 120 frames per second, each frame lasts about 1/120 second (≈8.3 ms). Doubling the frame rate halves the time per frame. They are not directly proportional (increasing one does not move the other in the same direction), they are not independent (changing the frame rate changes the time per frame), and they are not equal (fps has units of 1/second while time per frame has units of seconds per frame, so they’re not the same quantity).