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 related to chemistry, in a way that physics is also concerned about how atoms and molecules react, or in other words, move, when subjected to pressure and another chemical. The fizzing, bubbling, and smoking of substances, we can apply the laws of physics to these. Physics can be associated practically with everything.