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.
Chemistry is the study of matter and how matter changes. When chemists watch chemicals explode they are actually studying how those chemicals change, into light, sound, and heat specifically, when they are combined. There are five main types of chemistry: physical, analytical, biochemical, organic, and inorganic. The different types focus on different aspects of matter.