When the computer receives a rich signal (high voltage) from the O2 sensor, it leans the fuel mixture to reduce the sensor's reading. When the O2 sensor reading goes lean (low voltage), the computer reverses again making the fuel mixture go rich.
Chemistry and physics are branches of science that both study matter. The difference between the two lies in their scope and approach. Chemists and physicists are trained differently, and they have different professional roles, even when working in a team.
Physics is the study of matter, energy, and their interactions with one another. Physics seeks to study the world around us, the world inside us, and the world beyond us. It is the foundation of all other natural sciences, including chemistry, biology, oceanography, geography, and radiography.